Extraoral force-applying orthodontic appliance

ABSTRACT

An extraoral force-reaction device engageable with the wearer&#39;s head and/or neck, such as a headcap or a neckband, is connected to an intraoral force-applying device, such as molar bands, by force-producing means, such as springs. Snapback of the force-applying means is restricted by limiting the normal range of movement of the force-applying elements and such snapback is controlled in response to relative movement of the intraoral means and the extraoral force-reaction means away from each other beyond a predetermined maximum limit, or in response to stressing of the force-producing means beyond a predetermined maximum degree of force exerted by the force-producing means. Snapback control may be effected by latching of a limit latch to prevent or limit return movement of the force-reaction device and the force-applying device, or disconnectible means can be disconnected to interrupt the application of primary force to the intraoral means and reaction force to the head or neck engageable means. The force to be exerted by the spring force-producing means can be readily adjustable in predetermined increments, such as by engagement of different holes in a spring anchor strap with an anchor pin, or by a linear ratchet device except where the force-producing means is of a negator type which will produce a constant force in various adjusted positions of the negator force-producing means relative to the reaction device and the force-applying device. Also, various components of the extraoral force-reaction device can be assembled and adjusted as to length by connection of separable connections, which may include linear ratchet means.

This application is a continuation-in-part of my application Ser. No.655,401, filed Feb. 5, 1976, for Extraoral Force-Applying OrthodonticAppliance, which is a continuation-in-part of my application Ser. No.613,243, filed Sept. 15, 1975 and now abandoned, for ExtraoralForce-Applying Orthodontic Appliance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This application relates to orthodontic appliances capable of applying aprimary force to a jaw, the reaction from which force is applied to theexterior of the head and/or neck by an extraoral force-reaction device.

2. Prior Art

A device for applying primary force to a jaw by an intraoral device andexerting the reaction force on an extraoral force-reaction deviceengageable with the wearer's head or neck is shown, for example, in theArmstrong U.S. Pat. No. 3,526,035. The appliance of the presentinvention constitutes an improvement over the apparatus shown in thatpatent. A device for applying a constant force to an intraoral deviceutilizing a negator is shown in McVickers et al. U.S. Pat. No.3,686,757. Patents showing orthodontic headgear including yoke bows areInterlandi U.S. Pat. No. 3,203,099 and DeWoskin U.S. Pat. No. 3,571,930,FIG. 3.

The Problem

The problem which has not been solved by prior orthodontic devices hasbeen provision of protection against injury by snapback of the intraoraldevice should the intraoral device be pulled from the patient's mouthand released while it is still connected to the force-producing unit, oreven if the tips of such device were merely disengaged from their toothband sockets and the device then released while such tips are still inthe mouth. Such snapback could occur by a patient improperly removingthe device, or by childish pranks, or by a part of the headgear beingcaught by either a stationary or a moving object. This problem has beenrecognized as discussed in Snead U.S. Pat. No. 3,903,604 at column 1,lines 21 to 31, for example. Even if the tips of such device were notpulled from the tooth band sockets a yank on the headgear resulting fromsuch catching would cause discomfort and possible injury.

A principal object of the present invention is to provide effectivecontrol over the snapback of a force-producing unit applying a sustainedyieldable force to a jaw such as by intraoral gear used in orthodontictreatment. More specifically, it is an object to exercise such snapbackcontrol when extraoral force-reaction gear engageable with the wearer'shead and/or neck and force-applying gear are separated more than apredetermined amount, or a force is exerted between such gear componentsof more than a predetermined magnitude.

A further object is to provide such control over the force-producingmeans without appreciably restricting the excursions of which the lowerjaw and head are capable.

If normal corrective force-applying operation of the gear is interruptedby control action on the force-producing unit, it is an object to enablethe gear to be rearranged or restored to its operative condition quicklyand easily.

Another object is to provide in an orthodontic appliance havingextraoral force-reaction and intraoral force-applying components aforce-producing unit which will produce a sustained, substantiallyconstant, predetermined force on a jaw, such as by a preliminarilystressed spring, which force-producing unit can be adjusted quickly andeasily to produce different predetermined degrees of force over a widerange while having a comparatively restricted range of movement for anyselected predetermined force.

An additional object is to provide an orthodontic headgear applianceincluding separate components that can be asembled readily andcomponents of which can be selected to fit patients having heads ofdifferent size.

It is a particular object to provide a disconnectible connection betweenextraoral force-reaction gear and intraoral force-applying gear which isvery precise and which will be disconnected immediately if apredetermined force which it is set to withstand is exceeded onlyslightly, and which gear components can be disconnected by a smallamount of relative movement. Such disconnection will occur whenever theextraoral force-reaction gear is pulled excessively, whetherintentionally or inadvertently, or is merely caught and the wearerexerts the force exceeding the predetermined force.

It is also an object to provide orthodontic gear having the foregoingcapabilities which is light, compact, durable, of simple and economicalconstruction and which can be fitted quickly, easily and accurately tothe patient.

The foregoing objects can be accomplished by orthodontic gear includingintraoral force-applying and extraoral force-reaction componentsconnected by a component connector including a force-producing componentwhich normally is yieldable relative to either the intraoralforce-applying component or the extraoral force-reaction component butwhich has a restricted range of operating movement, and which can eitherbe immobilized relative to the intraoral component or the extraoralcomponent, or freed from the intraoral component or the extraoralcomponent, such as by disconnection, so that the force-producing unitcannot snap back to produce sudden and violent relative contraction ofthe intraoral force-applying component and the extraoral force-reactioncomponent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1, 2, 3 and 4 are side elevations of a patient shown wearingdifferent types of orthodontic appliances to which the present inventionpertains.

FIG. 5 is a side elevation of a representative component connector ofheadgear shown in FIGS. 1, 2 and 3, on an enlarged scale, and havingparts broken away. FIG. 6 is a longitudinal section through suchcomponent connector, shown connected to intraoral force-applying gear.FIG. 7 is a longitudinal section through a portion of the componentconnector on a further enlarged scale.

FIGS. 8, 9 and 10 correspond respectively to FIGS. 5, 6 and 7, but showparts in a different relationship

FIGS. 11 and 12 are longitudinal sections corresponding to FIGS. 6 and7, respectively, and to FIGS. 9 and 10, respectively, but show parts ofthe component connector in another relationship. FIG. 13 is alongitudinal section corresponding to FIGS. 7, 10 and 12 with the partsin still another relationship. FIG. 14 is a longitudinal sectioncorresponding to FIGS. 6, 9 and 11, but shows portions of the connectorin still a different relationship.

FIG. 15 is a longitudinal section through the component connector shownin FIGS. 5 to 14, inclusive, with the various parts in explodedrelationship. FIGS. 16, 17, 18 and 19 are longitudinal sections througha portion of the component connector illustrated in FIGS. 5 to 15,inclusive, illustrating progressive stages in the assembly of the partsshown separated in FIG. 15.

FIG. 20 is a longitudinal section through a portion of a componentconnector corresponding to FIG. 19, but modified to provide a longerstroke of the parts, the construction of FIG. 19 being more suitable forutilization with a headcap such as shown in FIGS. 2 and 3, and theconnector of FIG. 20 being more suitable for combination with a neckbandsuch as shown in FIGS. 1 and 3.

FIG. 21 is a top perpsective of a component connector of the samegeneral type as shown in FIGS. 5 to 19, inclusive, but having a slightlymodified construction. FIG. 22 is a top perspective of the componentconnector shown in FIG. 21, with parts in exploded relationship.

FIG. 23 is a fragmentary top perspective of a component connectorshowing an alternative type of construction. FIG. 24 is a topperspective corresponding to FIG. 23, showing another alternative typeof construction.

FIG. 25 is a top perspective of a component connector with parts brokenaway, showing a modification of the construction of FIG. 21. FIG. 26 isa top perspective of the component connector shown in FIG. 25, buthaving the parts in exploded relationship. FIG. 27 is a fragmentary topperspective of the component connector of FIGS. 25 and 26, showing partsin a different relationship.

FIG 28 is an enlarged top perspective of a fragment of the componentconnector shown in FIGS. 25, 26 and 27, showing details of construction.FIG. 29 is a top perspective of the same structure as shown in FIG. 28,but with parts in a different relationship.

FIG. 30 is a longitudinal section through a fragment of a componentconnector corresponding to the connector fragment shown in FIG. 28, butof modified construction.

FIG. 31 is a longitudinal section through a fragment of a componentconnector corresponding to the fragment shown in FIG. 28 and FIG. 30,but illustrating a further modified type of construction.

FIG. 32 is a longitudinal section, FIGS. 33 and 34 are top perspectives,and FIG. 35 is a longitudinal section of different detailedmodifications of portions of a component connector.

FIG. 36 and FIG. 37 are side elevations of a fragment of a componentconnector, showing parts in different relationships, and FIG. 38 is atop perspective of the same fragment of a component connector with partsin still a different relationship.

FIG. 39 is a side elevation, and FIGS. 40, 41, 42 and 43 arelongitudinal sections through a portion of a component connector ofanother type, the several figures showing parts in differentrelationships. FIG. 44 is a transverse section taken on line 44--44 ofFIG. 41. FIG. 45 is a top perspective of the same portion of thecomponent connector showing the parts in exploded relationship.

FIG. 46 is a side elevation of a different type of component connector,certain features of which are similar to corresponding features of thecomponent connector shown in FIGS. 25 and 26; FIG. 47 is a longitudinalsection through such connector; and FIG. 48 is a transverse sectiontaken on line 48--48 of FIG. 47.

FIG. 49 is an edge elevation of a modification of the type of componentconnector shown in FIGS. 46, 47 and 48.

FIG. 50 is a side elevation of a component connector abutting adifferent type of force-producing element, and having parts broken away.FIG. 51 is a longitudinal section through such connector.

FIG. 52 is a side elevation of a component connector having still adifferent type of force-producing member, parts being broken away.

FIG. 53 is a plan of a preferred type of component connector with partsbroken away, FIG. 54 is a top perspective of such a connector, and FIGS.55, 56 and 57 are plans of such connector with parts broken away, suchviews showing parts of the connector in progressively differentrelationships.

FIG. 58 is an edge view of a component of the connectors shown in FIGS.53 to 57, inclusive.

FIG. 59 is a top perspective of a component connector utilizing anegator as a force-producing member. FIG. 60 is a longitudinal sectionthrough such component connector.

FIG. 61 is a longitudinal section through a modified type of componentconnector utilizing a negator as the force-producing member, parts beingbroken away, and FIG. 62 is a top perspective of such component withparts broken away.

FIG. 63 is a longitudinal section through still a different type ofconnector utilizing a negator as the force-producing member.

FIG. 64 is a top perspective of a further J-hook type of force-producingunit and headcap combination. FIG. 65 is an enlarged plan of theforce-producing unit with parts broken away. FIG. 66 is an enlargedfragmentary longitudinal section through the connection between theforce-producing unit and the headcap, and FIG. 67 is an elevation ofsuch connector seen from the right end of FIG. 66. FIG. 68 is alongitudinal section corresponding to FIG. 66 showing parts in adifferent relationship.

FIG. 69 is a top perspective of a connector of the type shown in FIGS.64 to 68 connecting a force-producing unit to a different type ofheadgear.

FIG. 70 is an enlarged longitudinal section corresponding to FIG. 66through a different type of connector, and FIG. 71 is a similar viewshowing parts in a different relationship.

FIG. 72 is a top perspective of a different type of force-producingJ-hook unit and a modified connector for connecting such unit to aheadgear.

FIG. 73 is an enlarged longitudinal section through the force-producingunit of FIG. 72. FIG. 74 is a top perspective of the force-producingunit shown in FIGS. 72 and 73 on an enlarged scale, parts being shown inexploded relationship and portions being broken away.

FIG. 75 is a top perspective of a different type of headgear andconnection adapted to be connected to a force-producing unit of the typeshown in FIGS. 72, 73 and 74. FIG. 76 is a transverse section through aportion of the headgear shown in FIG. 75 with a connector componentattached to it shown on an enlarged scale.

FIG. 77 is a top perspective of a portion of headgear of the generaltype shown in FIG. 75 but somewhat modified for connection to it of aforce-producing unit of the type shown in FIGS. 72, 73 and 74.

DETAILED DESCRIPTION

Orthodontic gear including an extraoral force-reaction componentengageable with the wearer's head and/or neck and a force-applyingcomponent, such as an intraoral component, of various types have beenused; representative types of gear are illustrated in FIGS. 1, 2 and 3.In each instance the gear includes two or three principal components,namely a force-applying component, by which a force is applied to a jaw,and an extraoral force-reaction band component, by which a reactionforce is applied to the head and/or neck, and one or two componentconnectors which usually include a force-producing unit for producing asustained force applied to the force-applying component. The term"intraoral" as used in the following description and claims is intendedto include force-applying devices for orthodontic treatment whichcontact the exterior of the lower jaw, such as a chin cup.

In FIG. 1 the extraoral force-reaction component includes a neckband 1,a tie rod 2 connected to the intraoral component, and a force-producingconnector unit 3. In FIG. 2 the extraoral force-reaction gear includesthe headcap 4 composed of a lower band 4a extending around the back ofthe head and an upper band 4b extending across the top of the head. Theends of these bands are connected together and to the rearward end ofthe force-producing connector unit 3. In FIG. 3 the neckband 1 and theheadcap 4 have individual force-producing connector units 3 which may beof the same type, and both of which are connected to the tie rod 2.

The force produced by the force-producing unit 3 in each instanceapplies a pull on the tie rod 2, which exerts a corresponding rearwardforce on the intraoral, or force-applying, component of the headgear towhich the tie rod 2 is connected. It is evident that the pull producedby the neckband type of gear shown in FIG. 1 is downward and rearwardfrom the mouth, whereas the pull produced on tie rod 2 by the headcaptype of extraoral gear shown in FIG. 2 is upward and rearward from themouth. By utilizing a combination of the neckstrap and the headcap asshown in FIG. 3, and arranging for the headcap force-producing connectorunit and the neckband force-producing connector unit to producepredetermined forces of desired magnitude, the direction as well as thedegree of pull exerted on the tie rod 2 can be selected over aconsiderable range.

FIG. 4 illustrates diagrammatically various vectors representingdifferent directions in which the pull on the tie rod 2 can be exertedby appropriately adjusting or setting the force-producingcharacteristics of the neckband and headcap force-producing units 3 andthe lengths of connections between such force-producing units and thetie rod. If the headcap force-producing unit is adjusted to produce onlya small force, the pull will be produced primarily by the neckbandforce-producing unit 3, so that the pull applied to the tie rod 2 willbe primarily along the vector Fa. Alternatively, if the force-producingunit 3 of the neckband is adjusted to produce little or no force, thepull on the tie rod 2 will be exerted almost entirely by the headcapforce-producing unit 3 and will act generally along the vector Fb. Ifthe forces produced by the neckband force-producing unit 3 and the forceproduced by the headcap force-producing unit 3 are approximately equal,the resulting pull on the connector component 2 will be along a vectorFc approximately bisecting the angle between the force lines Fa and Fbextending through the neckband force-producing unit and the headcapforce-producing unit, respectively.

By increasing the force produced by the neckband force-producing unit 3somewhat and/or decreasing the force produced by the headcapforce-producing unit 3 somewhat, the direction of pull on the tie rod 2can be lowered, such as to the vector Fd. Alternatively, if the headcapforce-producing unit 3 is arranged to provide an increased force and/orthe neckband force-producing unit 3 is arranged to provide a reducedforce, the direction of pull on tie rod 2 can be raised somewhat, suchas to the line of vector Fe. If the force produced by the neckbandforce-producing unit 3 is increased to a greater extent and/or the forceproduced by the headcap force-producing unit 3 is reduced farther fromequality, the vector of the pull on tie rod 2 can be lowered from themedian vector Fc below the vector Fd, such as to the vector Ff.Alternatively, the headcap force-producing unit 3 can be arranged toproduce a considerably greater force and/or the neckband force-producingunit 3 can be arranged to produce a considerably smaller force, so thatthe vector of the pull on tie rod 2 can be raised from the median vectorFc beyond the location of the vector Fe, such as to the location of thevector Fg.

In order to be able to arrange the pull on the tie rod 2 in differentdegrees and in different directions as discussed above, it is desirablefor the force-producing units to be constructed for easy substitution inthe gear or for easy adjustment to produce different degrees of force.Also it is important that the gear be designed so that snapback of theforce-producing unit can be controlled reliably to avoid sudden orviolent return contraction of the component applying the reaction forceto the head or neck and the component through which the force is appliedto the wearer's jaw. As an additional feature it is desirable to enablethe various components of the headgear to be connected readily anddisconnected at will or automatically in response to relativedisplacement of components more than a predetermined amount.

The principal features of the invention can be incorporated in aconnector which connects an extraoral force-reaction band member, suchas a neckband 1 or a headcap band structure 4a, 4b, with a tie rod 2, bywhich the pulling force is applied to intraoral force-applying gear.FIGS. 5 to 18 show one type of connector. Such connector includes aforce-producing unit 3 having a backing 5 that can be attached suitablyto the reaction force band component by being bonded or stapled to suchcomponent, as illustrated generally in FIGS. 1, 2, 3 and 4, and by thedot-dash line illustration of band means 4 in FIGS. 6, 9 and 14.Preferably the force-producing means carried by the backing 5 isenclosed in a housing tube 6. In the force-producing unit of FIGS. 5 to19, the force-producing means is shown as a helical tension spring 7,slidable within the tube 6. The force-producing unit can be connected tothe tie rod 2 by a side strap 8, having apertures 9 at regularly spacedintervals along its length for engagement by a hook on the end of thetie rod. The purpose of having a plurality of apertures in the strap isto enable the tie rod hook to be engaged in the appropriate aperture sothat the proper length of connection between the force-producing unitand the tie rod for the particular patient can be selected.

Instead of the strap 8 being connected directly to the spring 7, it ispreferred that an intermediate strap 10 be interposed between the strap8 and the spring. The end of such intermediate strap adjacent to thespring is connected to a hook on the end of the spring by a connectinghook 11 preferably made of resilient strip metal or plastic. The shankof hook 11 is apertured to engage the spring end hook. Thereversely-bent end of hook 11 passes through a slot in the end of theintermediate strap 10.

The hook 11 serves not only to connect the end of intermediate strap 10to the adjacent end of spring 11, but such hook can serve the additionalpurpose of controlling snapback of the spring under certain conditions.During normal use of the appliance, as illustrated in FIG. 6, theintermediate strap extends beneath a bridge 12 upstanding from andintegral with the backing 5 which preferably is of molded plasticmaterial. As the strap 8 and intermediate strap 10 are pulled to theright relative to the backing 5 from the normal operating position shownin FIG. 6, the hook 11 will be pulled toward the bridge 12 until anupwardly bowed leaf part 13a of the return portion of the hook 11 isengaged with the bridge, as shown in FIG. 9.

The hook 11 is sufficiently flexible so that the upwardly bowed portion13a can be depressed to enable that portion of the hook to be pulledbeneath the bridge from the position of FIG. 9 to the position of FIG.10. In order to contract the spring hook to this extent, it is necessarythat the pull on the spring exceed the normal operating pull. Theoperating pull could, for example, be as much as 32 ounces and the pullrequired to slide the hook from the position of FIG. 9 to the positionof FIG. 10 could be four or five pounds, for example. The amount of pullrequired would depend upon the relative heights of the bridge 12 and thehook 11 and the flexibility characteristics of the hook and of thebridge.

When the hook 11 has reached the condition of FIG. 10, very littleadditional pull is required to slide the upward bulge 13a of the hook tothe right beyond the bridge to the position of FIGS. 11 and 12. When thehook has reached this position, if the pull on the strap 8 andintermediate strap 10 is relieved, the pulling force of spring 7 will beinsufficient to pull the hook back under the bridge 12. Consequently,the hook 11 will constitute a limit latch which, in the latched positionof FIGS. 11 and 12, will control the snapback of spring 7 byimmobilizing the spring to prevent contraction movement of the springfrom the position of FIG. 11, through the position of FIG. 10, to theposition of FIG. 6.

The limit latch 12, 13a will be engaged whenever the pull on tie rod 2is sufficient to move the bow 13a of spring 11 under the bridge 12 tothe position of FIG. 11. To effect such movement, the tie rod 2 musthave been moved relative to the force-producing unit 3 and the head orneck engaging band means beyond a predetermined distance. In order toeffect such relative movement between the tie rod and theforce-producing unit and band means, it will be necessary to apply aseparating force between the tie rod and the force-producing unitexceeding a predetermined value. Consequently the parts can beproportioned and spaced so that the limit latch will be latchedautomatically in response to predetermined relative displacement of thetie rod 2 and backing 5.

Moreover, the flexibility characteristics of the material of the hook11, the width and thickness of the hook strip material, the hookproportions, and the height of the bow 13 with respect to the height ofthe bridge 12 can be selected so that the bow of the hook will be movedfrom the position of FIG. 9, through the position of FIG. 10, to theposition of FIG. 11 automatically in response to exertion of apredetermined degree of separation force between the intermediate strap10 and the backing 5. While the force exerted by spring 7 on the hook 11in the position of FIG. 11 will be insufficient to move the hook back tothe left under the bridge 12, the bow 13a can be depressed sufficientlyby manual pressure applied to it so that the pull of spring 7,especially if aided somewhat by manual pushing, or in some instancesmanual pushing alone, will move the hook back under the bridge to theposition of FIG. 10, whereupon the spring can return the hook to theposition of FIGS. 6 and 7.

It is preferred that the backing 5 have a further bridge 14 at the sideof bridge 12 remote from spring 7. Such bridge is lower than bridge 12so that, while the hook 11 can pass under bridge 12, it cannot pass tothe right, as seen in FIGS. 11, 12 and 13, beneath bridge 14. To insurea positive stop between the intermediate strap 10 and the bridge 14, theleft end of such strap can be provided with abutments 15 projecting fromthe intermediate strap on opposite sides of hook 11 far enough to engagethe left side of bridge 14 positively, as shown in FIG. 13.

During movement of the hook 11 from the position of FIG. 6 to theposition of FIG. 9, the hook may tend to drag along the housing tube 6and to drag a portion of spring 7 along such tube. To preventappreciable lengthwise movement of the tube as a result of such draggingaction, a stop projection 16 can be provided upstanding from the backing5 for engagement by the tube end to limit its movement toward bridge 12.

While the limit latch 12, 13a will immobilize the spring 7 in thecondition of its maximum extension permitted by movement of theintermediate strap 10, the reaction force resisting band means 1 or 4will still be connected to the tie rod 2 by the force-producing unit 3.A pulling force might be exerted on the intraoral component of theappliance sufficient to deform a portion of the appliance inadvertentlyby application of a strong force to it. Consequently, it is desirablefor the tie rod 2 and the head or neck engaging force reaction bandmeans, such as the neckband 1 or the headcap 4, to be disconnectedautomatically in response to application of a pulling force to the tierod exceeding a value higher than the amount of pull required to latchthe limit latch mechanism. The degree of pull to disconnect the tie rodmight, for example, be seven pounds.

Disconnection between the tie rod 2 and the neckband or headcappreferably is accomplished by disconnecting the side strap 8 from theforce-producing unit 3. Such a disconnectible connection is shown inFIGS. 5 to 22, inclusive, as including the widened end portion 17 of theintermediate strap 10 remote from the end of such strap carrying theabutments 15. Such widened end portion has a bridge 18, which canreceive beneath it the side strap 8, as shown in FIGS. 8 to 12,inclusive. Spaced to the left of the bridge 18 and upstanding from theintermediate strap 10 is a stop rib 19 having a dual function. The leftside of such rib is engageable with bridge 14 to limit movement of theintermediate strap to the left, and its opposite side is engageable bythe adjacent end of the side strap 8 to limit its movement to the leftrelative to the intermediate strap 10.

The end portion of the side strap 8 remote from the tie rod 2 carries areturn-bent load-releasing strip spring, preferably of metal. Such stripincludes a return bend 20 extending through a slit in the end portion ofthe strap 8 and a bowed spring leaf 21 projecting outwardly from thestrap. The distance between the bridge 18 and the rib 19 is sufficientlygreat to accommodate the major portion of the length of the bowed leafspring strip 21, so that such spring strip will fit between the bridge18 and the rib 19, as shown in FIGS. 9, 10, 11 and 12, for example.

The flexibility of the bowed spring leaf 21 and the height of the bridge18 are arranged so that the spring can be depressed to the conditionshown in FIG. 13 by application of a pulling force to the tie rod 2 andside strap 8 of a predetermined value, such as the value of seven poundsmentioned above. When the bowed spring leaf has been depressed in thismanner to slide beneath the bridge 18, the side strap 8 can be movedeasily to the right from the position of FIG. 13 to the disconnectedrelationship of FIG. 14. Thus, while the intermediate strap 10 remainsattached to the force-producing unit 3 by the limit latch hook 11 or theabutments 15 and the bridge 14, the side strap 8 and the intermediatestrap 10 will be completely separated to disconnect the tie rod 2 fromthe head-engaging reaction force component such as the neckband 1 or theheadcap 4.

FIGS. 5 to 14, inclusive, illustrate the parts of the force-producingunit 3 and representative intraoral gear in various relative positions.For purposes of illustration the intraoral gear is shown in FIGS. 6, 9,11 and 14 as including the inner bow 2a of a double face bow, the tierod 2 forming the outer bow. The inner tip 2b of the inner bow isreduced, as shown in FIG. 9, for insertion into the socket 2c of a molarband 2d, as shown in FIG. 6. If the face bow is grasped and pulled inthe direction indicated by the arrow at the right of FIG. 9, the tip 2bof the face bow will be pulled out of the molar band socket 2c, whilethe inner bow of the face bow remains in the mouth.

It will be evident that the displacement of the face bow from therelationship to the force-producing unit 3 shown in FIG. 6 to therelationship shown in FIG. 9 is quite small, but is adequate to providefor maximum movement between the force-producing unit and the face bowwhich could be accomplished by tilting of the head. Alternatively, whenthe head is erect or untilted, the face bow can be moved relative to theforce-producing unit to the position of FIG. 9 by grasping the face bowmanually and pulling in the direction indicated by the arrow in FIG. 9.While such manual movement is undesirable, the degree of displacement ofthe face bow from the teeth indicated in FIG. 9 would be insufficient towithdraw the inner face bow from the mouth. If the face bow werereleased, the force exerted on the side strap 8 by the force of spring 7acting on tie rod 2 would snap the double face bow inwardly farther intothe mouth, but the possible range of movement is quite small, i.e. thedistance that stop rib 19 could move to bridge 14, as shown in FIG. 9.Consequently, if inner tips 2b strike soft tissue in the mouth, nosubstantial injury would occur.

Before the face bow could be displaced from the force-producing unit 3sufficiently far to withdraw the inner bow 2a from the mouth, the limitlatch bow spring 13a would have been moved through the position shown inFIG. 10 at least to the position of FIG. 11. By such displacement thelimit latch bow spring 13a would have moved past the bridge 12, asillustrated in FIG. 11, to latched position. If the pull on the face bowwere released at that time, the face bow would not snap back appreciablybecause the latch 12,13a would have immobilized the spring 7 in thecondition shown in FIG. 11.

If the pulling force on the face bow were continued in the directionindicated by the arrow in FIG. 11, the tie rod 2 would be displacedfurther to pull the intermediate strap 10 from the position of FIGS. 11and 12 to the position of FIG. 13, in which the abutments 15 and/or thelatch bow spring 13a is engaged with the stop bridge 14. Continuedpulling would cause the bridge 18 of the intermediate strap to exert asufficient wedging action on the bowed leaf spring 21 to depress the bowfor movement into the position beneath the bridge 18 shown in FIG. 13.Further continued pulling on the face bow would cause the spring 21 toslide out from under the bridge 18, so that the side strap 8 would bedisconnected from the intermediate strap 10, as indicated in FIG. 14,and the face bow would be freely movable in the direction indicated bythe arrow in FIG. 14 relative to the force-producing unit 3.

Representative values of force to effect latching of the limit latch12,13a and to effect disconnection of the connection 18,21 have beenstated. It is also important to design the appliance so that the tie rod2 and the force-producing unit 3 are displaced through particulardistances to effect latching of the limit latch and disconnection of theseverable connection. It is desirable to enable the tie rod 2 and theforce-producing unit 3 to be moved relatively to a greater extent whenthe force-producing unit is mounted on the neckband 1 than when theforce-producing unit is mounted on a headcap 4 before the limit latchlatches or the disconnectible connection is disconnected.

A typical example for a headcap-mounted force-producing unit 3 wouldenable the tie rod 2 and such force-producing unit to move through adistance within the range of five to eight millimeters before the limitlatch bow 13 comes into contact with the bridge 12 in the position shownin FIGS. 9 and 10. This type of construction is illustrated in FIGS. 5to 18, and particularly in FIG. 19. The parts of the appliance shown inFIG. 20 are the same as the parts of the appliance shown in FIG. 19,except that the length of the backing 5 between tube stop 16 and bridge12 is somewhat greater than the distance between the stop and bridge inFIG. 19, and the length of the intermediate strap 10 between abutments15 and stop rib 19 is correspondingly greater. The extent of normalmovement permitted by the structure shown in FIG. 20 before the bow 13aengages the latch bridge 12 would be twelve to fourteen millimeters, forexample, instead of five to eight millimeters as in the case of aheadcap. The maximum yieldable extension and contraction relativemovement of the strap 10 and force-producing unit should not exceed 16millimeters, or a force change of twelve ounces, during such movement.The construction shown in FIG. 20 is more suitable for association witha neckband 1 to accommodate excursions of the lower jaw and the head.

Relative movement of the tie rod 2 and the force-producing unit 3 afterthe latch bow 13a comes into engagement with the latch bridge 12 inorder to secure the latch as shown in FIG. 12, would be the samewhatever normal relative movement of the tie rod and force-producingunit could occur prior to such contact of the latch bow with the latchbridge. The additional extent of relative movement to secure the latchcould be 3 millimeters, for example. In order to disconnect the sidestrap 8 and the intermediate strap 10 by relative movement of the bowspring 21 and the bridge 18 from the relationship shown in FIGS. 11 and12 to the relationship in which the bow spring has just cleared thebridge 18 beyond the position of FIG. 13, could be an additional fourmillimeters or less.

Thus relative movement of the tie rod 2 and the force-producing unit 3beyond the normal range of movement for a distance of 3 millimeterswould effect latching of the limit latch to immobilize spring 7 whetheror not a disconnectible connection is included. If the limit latch wereomitted, such as by omitting the bridge 12, the disconnectibleconnection could be disconnected by a movement of 4 millimeters or lessbeyond the normal range of movement. If both the limit latch and thedisconnectible connection are utilized, the latching of the limit latchand the disconnection of the connection would be accomplished byrelative movement of the tie rod and the force-producing unit through adistance of approximately 7 millimeters beyond the range of normalrelative movement of the tie rod and the force-producing unit.

It is important for the limit latch to be operated, or for the sidestrap 8 to be disconnected from the force-producing unit 3, or both,before the intraoral component of the orthodontic gear, including theinner bow 2a and the tips 2b, has been withdrawn completely from thewearer's mouth, or ideally before the inner bow tips have been withdrawnfrom the molar band sockets, so that snapback of the face bow caused bythe force-producing unit cannot occur when the inner bow of the doubleface bow is in a position such that snapping-back action of such bowmight cause the inner bow tips 2b to penetrate an external portion ofthe face. Consequently, the normal range of relative movement of theside strap 8 and the force-producing unit 3 must be sufficiently smallso as to initiate latching action of the limit latch to immobilize thespring 7, and/or to effect disconnection of the side strap 8 from theforce-producing unit 3, before the inner bow 2a and tips 2b have beenwithdrawn completely from the mouth of the wearer, such as when theinner bow has not been pulled appreciably farther outward from the mouththan the position of the inner bow shown in FIG. 11.

Both to latch the limit latch and to disconnect the side strap 8 fromthe intermediate strap 10 will, of course, require a greaterdisplacement of the intraoral device from the force-producing unit 3beyond the normal range of movement of these parts. Where a limit latchand a disconnectible connection are arranged in series, therefore, therange of movement of the intraoral device relative to theforce-producing unit should be as small as reasonably possible, whilestill affording sufficient relative movement between the side strap 8and the force-producing unit 3 to enable the hook of the tie rod 2 to beengaged in the appropriate hole 9 of the side strap 8 and to accommodatereasonable excursive motion of the lower jaw relative to the headwithout effecting latching of the limit latch or disconnection betweenthe side strap 8 and the force-producing unit 3.

The strap 10 is shown in FIGS. 5, 6 and 7 in approximately the middle ofits operating range. If pull on the side strap 8 were completelyrelaxed, the force produced by spring 7 would pull the intermediatestrap 10 to the left, as seen in FIGS. 5, 6 and 7, until the stop rib 19is drawn into abutment with the right side of the low bridge 14. Theother extreme of the normal range of relative movement of the tie rod 2and force-producing unit 3 is reached when the bow spring portion 13a ofthe hook 11 is engaged with and starts to be drawn under the bridge 12of the limit latch mechanism.

With the parts of the orthodontic appliance in the normal treatingrelationship of FIGS. 5, 6 and 7, the spring 7 of the force-producingunit would exert a sustained and substantially uniform force on the facebow 2,2a directed inwardly of the mouth. As explained in connection withFIGS. 1 to 4, inclusive, it may be desirable to alter the force appliedto the face bow for treating different orthodontic conditions. While thespring 7 could be preliminarily stressed to produce substantially apredetermined force for application to the intraoral device, so that theforce produced could be altered by selecting different preliminarilystressed springs, the force-producing unit 3 shown in the appliance ofFIGS. 5 to 22 can be adjusted so as to produce different degrees offorce.

To provide for selective adjustment of the spring 7 by increments over aconsiderable range of selectible average treatment forces, the end ofspring 7 remote from the hook 11 is attached to one end of an anchorstrap 22. This anchor strap carries buttress teeth 23 spaced along itslength distances corresponding to increments of force, for which forceincrements the stress of and force produced by spring 7 can be alteredwithout changing appreciably the variation in force which occurs as aresult of relative movement of the tie rod 2 and the force-producingunit 3 during normal use of the gear. The abrupt sides of such teethface the spring so that they can engage an edge of a bridge 24 remotefrom the spring formed by a band having its length extendingtransversely of the anchor strap 22, beneath which bridge the anchorstrap can extend. The end portion of anchor strap 22 remote from spring7 can be confined by tucking it through a keeper slot 25 in the backing5 at the side of the anchor bridge 24 remote from the spring 7.

The buttress-toothed anchor strap 22 and the bridge 24 upstanding fromthe backing 5 constitute a linear ratchet which can be adjusted to alterthe force produced by the spring 7. The end of the anchor strap remotefrom that spring is simply threaded beneath the bridge 24 and pulled sothat successive teeth 23 engage the bridge until the spring 7 has beenstressed to the extent necessary for the spring to produce the desireddegree of orthodontic treatment force which is appied to the intraoralcomponent of the appliance. The free end of the anchor strap is thentucked through the slot 25 of the backing 5.

The various parts of the force-producing unit 3 are shown in explodedrelationship in FIGS. 15 and 22. The procedure by which such parts canbe assembled into the force-producing unit shown in FIGS. 5 to 14 isillustrated in FIGS. 16, 17 and 18. The end of intermediate strap 10remote from its bridge 18 is threaded first beneath bridge 14 and thenbeneath bridge 12 carried by the backing 5. The spring-connecting hook11 can then be inserted through the slot in the end of the intermediatestrap, as indicated in broken lines in FIG. 16, and one hook of thespring 7 can be threaded through the aperture of hook 11.

Next the aperture of the anchor strap 22 can be engaged with the hook onthe other end of the spring, and the housing tube 6 can then be slippedlengthwise over the anchor strap and the spring into the position shownin FIG. 17. Next the free end of the anchor strap 22 can be threadedbeneath the anchor bridge 24 and pulled to the left until the selectedtooth 23 of the linear ratchet corresponding to the desired force to beproduced by spring 7 has engaged the left side of the anchor bridge. Thetail of the anchor strap can then be tucked through the keeper slot 25as shown in FIG. 18.

Finally, the end of the side strap 8 remote from the load-releasingspring 20 is threaded beneath the bridge 18 of the intermediate strap 10in the direction indicated by the arrow in FIG. 18. When the left end ofsuch side strap has been seated between the bridge 18 and the stop rib19, as shown in FIG. 6 for example, the hook on the end of the tie rod 2can be engaged in an aperture 9 of such side strap, selected to providethe proper spacing between the neckband 1 or headcap 4 and the intraoralcomponent of the appliance, to enable the force produced by theforce-producing unit to be applied in the desired manner to theintraoral component. Any tag end of the side strap extending forwardlybeyond the aperture 9 in which the hook of the tie rod 2 is engaged canthen be cut off, if desired.

In providing a movement-limiting means, such as a limit latch, and/or adisconnectible connection for the side strap of an orthodonticappliance, consideration should be given to the amount of movement thatshould be afforded for the side strap before the movement-limitingmeans, such as a limit latch, is actuated or the disconnectibleconnection is disconnected, which considerations have been discussedabove. Because of excursions of the head and upper jaw relative to theneck, excursions of the lower jaw relative to the head and excursions ofthe lower jaw relative to the neck, more lengthwise movement of the sidestrap 8 should be permitted before the latch is latched or theconnection is disconnected if the force-producing unit is used inconjunction with a neckband 1 than would be required where theforce-producing unit is used in connection with a headcap 4. Acomparison of the structures shown in FIGS. 19 and 20 indicates thealteration in design which will provide a greater range of normalmovement between the side strap 8 and the force-producing unit 3 for aneckband installation than for a headcap installation.

As has been discussed above, contraction movement of the spring 7 to theleft is limited by engagement of the stop rib 19 on the intermediatestrap 10 with the right side of the low bridge 14. In FIGS. 19 and 20the stop rib 19 is the same distance from the low bridge 14, indicatingthat normal pull is being applied by the spring 7 through the side strap8 to the tie rod 2. Movement of the intermediate strap 10 to the right,both in the construction of FIG. 19 and in the construction of FIG. 20,is limited by engagement of the limit latch bow spring 13a with the leftside of the bridge 12.

The structure of FIG. 19 is intended for use with a headcap 4, and thestructure of FIG. 20 is intended for use with a neckband 1, because inFIG. 19 the bridge 12 is closer to the tube stop 16 than it is in FIG.20. Consequently, the latch bow spring 13a can move farther to the rightfrom the position shown when the structure of FIG. 20 is used than wherethe structure of FIG. 19 is used. The extent of the normal range ofmovement of the side strap 8 relative to the force-producing unit 3 canbe altered simply by changing the length of the interval betweenabutments 15 and stop rib 19 of the strap 10 and locating bridge 12farther from or closer to the tube stop 16 to alter the position of theadjacent end of spring 7 at opposite ends of the normal range ofmovement of the side strap 8.

While FIG. 9 shows the abutments 15 as passing beneath the crossbar ofthe bridge 12, the central portion of the bridge can be stiffened toreduce its deflection and notches can be provided beneath the oppositeends of the bridge crossbar to permit passage of the abutments 15, asshown in the bridge 12' of FIGS. 21 and 22. The bow spring 13a of thelimit latch would engage the thickened central portion of the bridgecrossbar and be depressed, whereas the abutments 15 spaced transverselyof the intermediate strap 10, as shown best in FIG. 22, would passthrough the downwardly opening notches in the opposite end portions ofthe bridge crossbar but engage bridge 14 to provide a positive stop.With the exception of this modification, the appliance shown in FIGS. 21and 22 is similar to that of FIGS. 5 to 20, inclusive.

FIG. 23 shows an alternative type of keeper arrangement for the tail ofthe spring anchor strap 22. In this instance the anchor strap is held inposition by an upright anchor pin 26 upstanding from the backing 5 andsubstantially straight throughout its length. Such pin is engaged in anaperture 23' selected from one of a row of apertures arranged along thelength of the spring anchor strap corresponding to different selectedforce-producing stresses of the spring 7. The anchor pin can lean tosome extent toward or away from the spring 7, as may be preferred formost convenient engagement of an aperture in the strap with the pin.

At the side of the anchor pin 26 remote from spring 7, arranged inseries relationship, are two or more cantilever bridges 24' mountedalternately at opposite sides of the strap. At the side of the strapopposite the root of each cantilever bridge is a wedge-shaped side stop27 spaced transversely of the backing 5 to some extent from the tip ofthe cantilever bridge. The tip of each bridge has an under bevel on askew angle, inclined toward the spring and the root of the bridge. Suchcombination of side stops and cantilever bridges enables the tail of theanchor strap beyond the anchor pin to be swung to and fro, first towardthe stop 27 nearest the anchor pin 26, next in the opposite directionwhile being slid up the inclined side of such stop and down under thecooperating cantilever bridge 24', and then in the opposite direction tobe slid up the inclined side of the next farther removed stop 27 anddownward to be caught under the cantilever bridge 24' cooperating withthat stop.

While any number of cooperating stops and cantilever bridges could bearranged in series lengthwise of the anchor strap, two such successivestops and cantilever bridges constitute a satisfactory keeper for thetail of the anchor strap. The adjacent end of the housing tube 6 for thespring 7 can be maintained in position centered relative to the keeperstructure by posts 28 upstanding from the backing 5 and spacedtransversely of the tube to receive its end between them as shown inFIG. 23. A particular advantage of this type of construction is that thetail of the anchor strap can be secured in any selected position ofadjustment simply by manipulation with the fingers. By holding the tailof the anchor strap in the proper longitudinally adjusted position as itis slid up the ramp of the first stop 27 and tucked under the firstcantilever bridge 24', the desired aperture 23' can be pressed down overthe anchor pin 26. The portion of the anchor strap tail beyond the firstkeeper element can then be swung farther in the same direction and backto be engaged with the next keeper element.

In the modified keeper construction shown in FIG. 24, a single keeperelement including the combination of a stop 27 and a cantilever bridge24' is combined with a keeper slot 25 through which the end portion ofthe anchor strap tail is tucked after the tail has been initially caughtunder the cantilever bridge 24' of the first keeper element. In thismodification the end of the housing tube 6 is shown as being held downmore positively by a band 29 bridging the end of the tube instead oflateral movement of the tube end being restrained simply by being lodgedbetween posts 28 as shown in FIG. 23.

In the force-producing unit 3 shown in FIGS. 25 and 26, the centralportion of the spring housing tube 6 is confined by a wider band 29'located generally centrally of the backing 5. Such band will deterbuckling of the tube by the force of a stressed spring 7 even if thematerial of the tube is quite flexible. Also in this modification only asingle keeper element including a stop 27 and a cooperating cantileverkeeper bridge 24" is shown. Such cantilever bridge, however, is longerthan the bridges 24' shown in FIGS. 23 and 24, so as to confine the tailof the anchor strap more reliably than would a single keeper element ofthe type shown in FIG. 23.

The connection of the side strap 8 to the force-producing unit 3 shownin FIGS. 25 to 29, inclusive, like that described in connection withFIGS. 5 to 22, has both a limit latch and a disconnectible connection.The disconnectible connection including the bowed spring leaf 21cooperating with the bridge 18 is the same as that described inconnection with the apparatus of FIGS. 5 to 22. FIG. 27 shows how theside strap 8 can be assembled with the intermediate strap 10, as alsoillustrated in FIG. 18.

The limit latch structure shown in FIGS. 25 to 29 differs from the limitlatch structure of FIGS. 5 to 22 in that a molded buttress tooth 13b issubstituted for the bow spring 13a of the limit latch of FIGS. 5 to 22.Preferably the backing 5 and the intermediate strap 10 of FIGS. 25 and26 are molded of plastic material. An inclined or sloping side of thebuttress wedging member 13b will engage with the left side of the latchbridge 12". Bridge 12" also serves as a stop for the end of tube 6 asthe side strap 8 is pulled in the direction indicated by the arrow inFIG. 25. Such buttress tooth 13b and/or the bridge 12" will besufficiently yieldable to enable the buttress tooth to be pulled beneaththe bridge when a force of predetermined maximum value is applied to theside strap 8 and to the force-producing unit 3 tending to separate them.

When the buttress tooth 13b has been pulled beneath the bridge 12" tothe side opposite that shown in FIG. 25, the force of the spring 7 willbe insufficient to pull the abrupt or sheer side of such tooth backunder the bridge. The shoulder 15' of the enlarged end of theintermediate strap 10, with which enlarged end the spring is engaged,will abut the left side of the bridge 12" after the buttress tooth 13bhas passed to the right of such bridge to prevent the intermediate strap10 and the spring 7 from being extended relative to the backing 5 to agreater extent. The buttress tooth 13b can be moved manually at willback under the bridge 12" from the latched position shown in FIG. 28 byswinging the intermediate strap 10 relative to the bridge as shown inFIG. 29. The corners of the buttress tooth 13b are clipped to providewedging chamfers that can be pushed against the right side of the bridgeto wedge it up sufficiently to enable the buttress tooth to move backbeneath the bridge to the position of FIG. 25.

In FIG. 30 a further modification of the limit latch is shown. In thisinstance a bow spring 13c is formed as an integral part of theintermediate strap 10. As in the types of limit latches describedpreviously, a sufficient pull on the intermediate strap to the right, asseen in FIG. 30, will effect a wedging action between the bridge 12" andthe bow spring 13c so that one or both of them will yield sufficientlyto enable the bow spring to pass to the right beneath the bridge 12"into latched position. Abutment of the shoulder 15' of the strap endwith the left side of the bridge will limit extension movement of theintermediate strap and the force-producing unit. To release the limitlatch, the bow 13c can be pressed downward manually and pushed to theleft so that, with the aid of the spring 7, the bow can be moved backbeneath the bridge 12" to the position shown in FIG. 30.

The parts are shown in FIG. 30 at the right end of the normal operatingrange. The left end of the operating range is established by engagementof the stop rib 19 with the right side of the bridge 12". Despite theability of the stop rib 19 to effect such stop action, the intermediatestrap 10 can be inserted beneath the bridge 12" from left to right asseen in FIG. 30 during initial assembly of the parts by effecting suchinsertion before the housing tube 6 is inserted over the spring 7,because, as will be seen in FIG. 30, the intermediate strap 10 is raisedby such tube to the extent of its thickness.

In FIG. 31 another modification of the limit latch is shown in which ametal strip 11', forming a bow spring 13d having a configurationdifferent from the hook 11 shown in FIGS. 5 to 22, has an end portionextending through transverse slots in an intermediate strap 10 generallyof the type shown in FIGS. 25 and 26.

A free end portion of the strip 11' can be depressed downward into aslot 11" extending lengthwise of the intermediate strap 10 to facilitatepassage of the bow spring 13d beneath the bridge 12" when strap 10 ismoved to the right as seen in FIG. 31. Movement of the intermediatestrap 10 to the right will be limited by abutment of the shoulder 15'with the left side of the bridge, and return movement of theintermediate strap from latched position of the latch will be preventedby the left side of the spring bow 13d engaging the right side of thebridge 12". The latch can be released by pushing the spring bow 13d backto the left of the crossbar of the bridge, which will also press thefree end of the strip 11' downward into the slot 11" of the intermediatestrap 10, so that such bow can pass beneath the bridge crossbar. Again,the normal operating range of movement of the intermediate strap 10relative to the force-producing unit 3 will be established between theposition shown in FIG. 31 and the position to the left at which the stoprib 19 is engaged with the right side of bridge 12".

Where the force exerted by the spring 7 in the various force-producingunits described above can be altered to provide the desired treatment,it is preferred that there be calibration means to indicate the degreeof force which is being produced by the spring in its different adjustedconditions. Such calibration means are shown in FIGS. 5, 8 and 21 to 27,as including a calibration scale 30 graduated in ounces, having linescorresponding to such graduations that are visible through thetransparent housing tube 6 for coordination with the end of the spring 7remote from the side strap 8. Thus in FIGS. 5 and 8 the spring 7 is setto provide an average working pull of sixteen ounces. In FIG. 21 thespring is set to provide an average working pull of 8 ounces. In FIGS.23 and 24 the spring is set to provide an average working pull of 32ounces.

Reference is made to the "average" working pull because considerablemovement of the side strap 8 relative to the force-producing unit 3occurs in the neckband type of appliance shown in FIG. 1 and the pull atone end of the working range will be different from the pull at theopposite end of the working range. Some range of movement is required tohook the tie rod 2 to the side strap 8. After such attachment, when thehead and lower jaw are held in the most usual position the right end ofthe spring 7 should be aligned with the zero index mark 31, as shown inFIG. 5. When the right end of the spring is aligned with such indexmark, the pull produced by the spring will be that designated by thecalibration line 30 aligned with the left end of the spring. When thespring moves to the left of the zero index mark 31 the pull of thespring will be somewhat reduced, as indicated by the minus signs at theindex 31. When the right end of the spring is pulled to the right beyondthe zero index mark, as indicated by the plus signs in FIG. 8, forexample, the pull produced by the spring will be greater than the lineof the calibrations 30 with which the left end of the spring is inregistration.

In any case the bridge 14, abutments 15 and stop rib 19 limit relativemovement of the intermediate strap 10 and the force-producing unit 3 inthe normal range of resilient movement to a distance less than theextent to which the spring anchor strap and the left end of the springcan be moved to alter the amount of average force produced by thespring. The operating range of the right end of the spring is usuallyfrom 6 to 12 millimeters and never over 16 millimeters, whereas the leftend of the spring should be adjustable over a range of 12 to 40millimeters to provide a desirable range of predetermined forces to beapplied to the tie rod 2.

In FIG. 32 a limit latch is combined directly with the side strap 8instead of an intermediate strap 10, and no disconnectible connection isprovided. The left end of the side strap 8 overlaps the right end of thebacking 5, and an enlargement 15" is provided on the left end of theside strap to which the right end of the spring 7 is connected directly.A stop rib 19' is provided on the backing 5, which is engageable by theleft end of the side strap 8 to limit relative contracting movement ofthe side strap and the backing 5 at the minimum pull end of the normalstroke. The maximum pull end of the normal stroke is reached when thelimit latch buttress tooth 13e comes into engagement with the left sideof the bridge 12, as discussed in connection with the operation of thelimit latch tooth 13b and the bridge 12" in the description of theappliance shown in FIGS. 25, 26 and 28.

In the form of the device shown in FIG. 32 a predetermined excessivepull applied to the tie rod 2 will move the buttress tooth 13e beneaththe bridge 12 to its right side, as shown. A ramp on enlargement 15"constituting a stop member will be engaged with the left side of thebridge 12 to prevent further extension movement of the side strap 8 andthe backing 5. The spring 7 will be immobilized when the parts havereached this condition. The buttress tooth 13e has clipped corners likethe corners of the tooth 13b shown in FIGS. 28 and 29. Consequently,when it is desired to release the limit latch, the side strap 8 can beswung relative to the backing in the manner indicated in FIG. 29, sothat the buttress tooth can move back to the left beneath the bridge 12.Initial assembly of the side strap 8 and the backing 5 can beaccomplished simply by threading the right end of the side strap beneaththe bridge 12 from left to right.

FIGS. 33, 34 and 35 show linear ratchet arrangements which can be usedto connect different components of the gear where it is desired to beable to establish different lengths of straps for different patients. InFIG. 33 such a linear ratchet arrangement is shown as being used toconnect the side strap 8 and an intermediate strap 10 of the type shownin FIGS. 25 and 26, while at the same time providing a connectiondisconnectible automatically in response to the occurrence of apredetermined excessive degree of pull. The linear ratchet includesbuttress teeth 32 molded integrally with the side strap 8. Thesebuttress teeth are of a height to snap successively beneath the bridge18 as the strap is pulled to the left relative to the intermediate strap10 in the direction indicated by the arrow.

When the desired length of strap 8 has been reached with an abrupt sideof a buttress tooth 32 engaging the left side of bridge 18, the end ofside strap 8 projecting to the left of the bridge 18 may be cut offappropriately so that the cut end will abut the stop rib 19 and leaveonly a single buttress tooth or member at the left of the bridge. Whenthe pull on the side strap 8 exceeds a predetermined value, the buttresstooth engaging the left side of the bridge 18 will wedge the bridgeoutward and be pulled beneath the bridge to disconnect the connectionbetween the intraoral component and the force-producing unit in themanner described above.

In FIG. 34 the linear ratchet construction is shown as being used toconnect a tail strap or tongue 33 provided on the end of backing 5remote from the side strap to an extraoral component reaction bandmember such as the headcap 4. A stop rib 34 is provided on such headcapso that, when the tail strap has been threaded beneath a latch bridge 35for a distance sufficient to provide the desired fit, the end of thetail strap projecting beyond such bridge can be cut off appropriately tofit between the bridge and the stop rib and to leave only a singlebuttress tooth or member at the left of the bridge. Excessive pullbeyond a predetermined value will cause the abrupt side of such memberto wedge the bridge outward and disconnect the connection afforded bythe linear ratchet tooth or buttress member 32 engaging the left side oflatch bridge 35.

Instead of providing the stop rib 19 as shown in FIG. 33, or the stoprib 34 as shown in FIG. 34, a suitable stop can be formed by providing asecond bridge 34' spaced to the left of bridge 18, as shown in FIG. 35.If this construction is used for tail strap 33, the second bridge 34'would replace the stop rib 34. With such a construction it would bedesirable for the bridge 34' to be made somewhat higher than the bridge18, so that the strap 8 could be pulled to the left to a desiredposition of adjustment more easily than it could be pulled to the rightto move a ratchet tooth under bridge 18. Again, when the desiredadjusted relationship between strap 8 and the bridge has beenestablished, the left end of the linear ratchet strap can be cut off sothat disconnection of the linear ratchet strap and the member carryingthe bridge can be accomplished by passage of a single buttress toothbeneath the bridge.

In FIGS. 36, 37 and 38 an alternative type of disconnectible connectionbetween the backing 5 and a head-engageable reaction component, such asthe headcap 4, is shown. By such connection headgear components ofdifferent size can be connected readily to the force-producing unit 3.In this instance the backing member has a short tail strap 33' or tongueinsertible beneath the bridge 35 when moved in the direction indicatedby the arrow in FIG. 38. The backing 5 carries a bowed leaf spring 36,preferably of strip metal, which can be depressed either directlymanually, or by wedging action by pushing the left end portion of suchspring against the right side of bridge 35 as seen in FIGS. 36 and 38.Such bowed leaf spring will snap up at the left side of bridge 35 whenthe left end of the tail strap 33' has reached a position adjacent tothe stop rib 34, as shown in FIG. 36. If an excessive pull is exertedbetween the force-producing unit 3 and the headcap 4, the connectionbetween the tail strap 33' and the headcap will be disconnected as shownin FIG. 37 by yielding of the spring 36 in the manner described inconnection with spring 21, as shown in FIGS. 13 and 14.

In the type of appliance shown in FIGS. 39 to 45, inclusive, theadjacent end portions of the side strap 8 and the intermediate strap 10'overlap between parallel walls 37, connected by a bridge 38. The lowerportions of such walls have barbed projections 39 insertable throughslots 40 in the end portion of the backing 5 adjacent to the tie rod 2.The walls 37 will have sufficient resilience to enable their lower edgesto be moved toward each other so that the side barbs of the projections39 will snap beneath the backing 5 to hold the barbs securely inengagement with the underside of the backing 5.

The end of the housing tube 6 adjacent to the walls 37 has a top bevel,and a notch 41 in its lower side is engageable with a block 42projecting upward from the backing 5 to prevent rotation of the tuberelative to the backing. The end of intermediate strap 10' has across-rib 43 integral with it and the cross-rib side 44 facing thespring 7 is steeply inclined. Such rib side is engageable with thecomplementally inclined side 45 of cross-rib 46 on the adjacent end ofthe side strap 8.

A hook on the end of spring 7 is engaged in a hole in the adjacent endof intermediate strap 10', so that the spring tends to pull the strap tothe left as seen in FIGS. 40 to 43. In the absence of any opposing forcethe intermediate strap will be pulled into the position of FIG. 40 andheld in that position by engagement of the inclined side 44 of thecross-rib 43 with the right edge of a crossbar 47 connecting the twoupright walls 37. With the intermediate strap in this position, the endof side strap 8 remote from the cross-rib 46 can be threaded between thewalls 37, beneath the bridge 38 and above the cross-rib 43 of theintermediate strap 10' in the manner illustrated in FIG. 40.

As the cross-rib 46 of the side strap 8 moves between the walls 37, theinclined side 45 of the downwardly projecting cross-rib 46 will engagethe upper portion of the inclined side 44 of the cross-rib 43 onintermediate strap 10'. As the side strap 8 is pulled to the right, theengagement of its cross-rib side 45 with the cross-rib side 44 ofintermediate strap 10' will pull the intermediate strap to the right inopposition to the force exerted by spring 7 as indicated in FIG. 41. Thepressure between the inclined sides 45 and 44 will tend to wedge the endof side strap 8 carrying cross-rib 46 upward. Engagement of the upperside of such strap with the bridge 38 will limit such upward movement.

A top lug 48 projects upward from the upper side of the side strap 8adjacent to the cross-rib end of such side strap, which lug isengageable with the right edge of the bridge 38 when the side strap andthe intermediate strap 10' have been pulled to the position of FIG. 42.The wedging action produced by the engagement of the steeply inclinedside 44 of cross-rib 43 and the steeply inclined side 45 of cross-rib 46will snap the end of the side strap upward to the position of FIG. 42,so that the lug will engage the edge of the bridge if the pulling forceof the tie rod 2 to the right is relieved. Such engagement of the stoplug with the bridge edge will immobilize the spring 7 so that thecross-rib sides 44 and 45, the stop lug 48 and the bridge 38 constitutea limit latch operating in the manner described above for limit latchesof other forms of the present invention.

If the pulling force exerted on the tie rod 2 increases appreciablybeyond that required to pull the side strap 8 and the intermediate strap10' to the positions shown in FIG. 42, the straps will be moved into thepositions shown in FIG. 43 in which the end portion of the side strap 8clears the bridge 38, whereupon the wedging force between the steeplyinclined cross-rib sides 44 and 45 will cause the end of the side strap8 to be slid upward to the broken-line position shown in FIG. 43. Insuch position the side strap will be free from the intermediate strap toeffect disconnection of the disconnectible joint. When the cross-rib 43is thus freed from the pulling force on the side strap 8, the stress ofspring 7 will snap the intermediate strap back to the left from theposition of FIG. 43, so that the cross-rib 43 will engage the stop bar47, as shown in FIG. 40, but such snapback movement of the intermediatestrap will cause no difficulty because the intermediate strap issubstantially completely enclosed within the housing formed by thebacking 5, the sides 37 and the bridge 38.

In order to insure that the steeply inclined faces 44 and 45 of thecross-ribs 43 and 46 are retained reliably in engagement until the leftend of the side strap 8 has been drawn beyond the right edge of bridge38, it is desirable to provide rails 49 inclined from their endsadjacent to spring 7 outwardly away from the backing 5, which rails areintegral with such backing. The ends of such rails can be connected byan end wall 50 which projects from the backing 5 beyond the edges of therails to form a stop flange engageable by the end of intermediate strap10' when it has reached its limiting position to the right as seen inFIG. 43.

The parts of the appliance shown in FIG. 45 can be assembled by firstmounting the element including walls 37 and bridge 38 on the backing 5by pushing the barbed projections 39 through the slots 40. Theintermediate strap 10' can then be moved into the chamber between thewalls 37 lengthwise from right to left, as seen in FIGS. 40 to 43,inclusive. Next the hook of spring 7 can be engaged with thespring-anchoring aperture of the intermediate strap, and the housingtube 6 can be slid over the spring until its notch 41 is engaged withthe block 42. Finally the side strap 8 can be threaded between the walls37 and beneath bridge 38 from left to right, as stated above and shownin FIG. 40.

The spring 7 of the appliance shown in FIGS. 39 to 45 can be of thepreliminarily stressed type, or the initial stress of the spring can beadjustable by the arrangement shown in FIG. 39. The anchor strap 22connected to the left end of the spring 7 can be secured to the backing5 by a headed pin 51 extending through an aperture 23' in the springanchor strap 22 and through the backing 5. To maintain the tube 6 inproper lengthwise position, the left end of such tube may have a tabintegral with it interposed between the anchor strap and the backing,which is also apertured for penetration by the securing pin 51.

The degree to which the spring 7 is stressed, and consequently themagnitude of the pull exerted by the spring on the tie rod 2, can bealtered by shifting the spring anchor strap 22 lengthwise to engage theheaded pin 51 in different apertures 23' in the spring anchor strap. Thefarther to the left such strap projects, the greater will be the stressof the spring 7, and correspondingly greater will be the pull exerted onthe tie rod 2. The magnitude of the spring stress can be indicated bycalibrations 30 with which the end of the anchor strap 22 can bealigned. As discussed in connection with FIG. 5, for example, thecalibrations can be in increments of eight ounces, and the calibrationscan be located to cooperate with the end of the anchor strap 22 toindicate the stress of the spring.

Alternatively, the calibrations can be placed on the anchor strap itselfopposite the respective apertures, as shown in FIG. 39 and designated30'. While the calibrations on the right side of the spring anchor strapsignify ounces of average pull on the tie rod 2, such spring anchorstrap can be used with various springs having different loadcharacteristics. All helical tension springs, however, have a deflectionrate corresponding substantially linearly to the pull exerted by such aspring. Especially if the anchor strap 22 is to be used in associationwith springs having different characteristics, the spring loadadjustment apertures can simply be numbered 1, 2, 3, 4 and 5, asindicated along the left margin of the spring anchor strap in FIG. 39.

The calibrations at the left of FIG. 39 are stated to indicate averagevalues of pull on the tie rod 2. The calibrations are arranged todesignate the exact value of the pull on such tie rod when the stop lug48 on the side strap 8 is in registration with the zero index mark 31'on the bridge 38. When such stop lug is at the left of the zero indexmark, the pull exerted on the tie rod will be somewhat less than thevalue indicated by a calibration 30 or 30'. Conversely, when the stoplug is at the right of the zero index mark 31', the pull on the tie rodwill be somewhat greater than that indicated by a calibration 30 or 30'.

The force-producing unit 3, shown in FIGS. 46, 47 and 48, is similar tothat shown and described in connection with FIGS. 25 and 26. In thisinstance, however, the side strap 8' carries the number 13b of the limitlatch and is connected directly to spring 7. The opposite end of strap8' is connected to the tie rod 2e by a swivel connector 52. In thisinstance the tie rod is in the form of a J-hook. The shank of suchJ-hook extends under bridges 53 arranged in series on the backing 5.Such backing is secured to a neckband 1, and an auxiliary headband 4c isattached directly to the backing to extend upward across the head justforward of the ear to deter sagging of the side portion of the neckband.

FIG. 49 also shows a force-producing unit 3 similar to that shown anddescribed in connection with FIGS. 25 and 26, but in this instance thehousing tube 6' is made of comparatively rigid transparent plasticmaterial of preformed shape, so that it will maintain its shape withoutprovision of the tube-retaining band 29' shown in FIGS. 25 and 26despite the spring 7 housed within it being preliminarily stressed orbeing stressed to a considerable degree by lengthwise extension ofanchor strap 22.

The force-producing unit 3' shown in FIGS. 50 and 51 utilizes a helicalcompression spring for producing the force applied to the intraoralcomponent of the appliance instead of a helical tension spring as usedin the appliances shown in FIGS. 5 to 49, inclusive. In this unit thecompression spring 7' is received in housing tube 6", and its right endis seated on an internal flange at the right end of such tube. The sidestrap 8 has an extension 8" connected to a plunger rod 54 extendingaxially through the spring and carrying a plunger head 55 engageablewith the left end of spring 7'.

The backing 5' has a row of holes 56 extending lengthwise of it, whichholes are spaced apart corresponding to increments by which thecompression spring 7' could be contracted to alter the force which itproduces and which is applied to the side strap 8. The housing tube 6"has a tab projecting from its left end remote from its internallyflanged end on which the spring 7' seats. This tab has in it an aperturewhich can be placed in registration with various backing apertures 56 bymovement of the housing tube 6" lengthwise of the backing forcorrespondingly altering the length of the spring. The tube 6" can besecured to the backing 5' in any desired longitudinally adjustedposition by inserting the shank of a headed retaining pin 51 through theaperture in the tube tab and an aperture 56 of the backing 5' inregistration with the tab aperture.

In FIG. 50 calibrations 30" on the backing 5' are shown, designatingounces of pull exerted on the side strap 8. The average pull will beindicated by the calibration line in registration with the right end ofthe housing tube 6'. Such calibration will indicate the exact pull onthe side strap 8 when the plunger head 55 is in registration with thezero index mark 31". If the side strap 8 has pulled the plunger head tothe right of such index mark, the pull on the side strap will becorrespondingly greater than the force indicated by the calibration inregistration with the right end of the tube 6', and if the side strap 8is drawn to the left as seen in FIG. 50, so that the plunger head 55 isat the left of the zero index mark 31", the pull on the side strap 8will be correspondingly less than the value indicated by the calibrationin registration with the right end of the tube 6'.

While the calibration lines 30" are shown in FIG. 50 as cooperating withthe right end of the housing tube 6', an additional or alternative typeof spring adjustment marking is shown by the numerals 1, 2, 3 and 4alongside the various apertures 56 of the row of apertures in thebacking 5'. Such digital calibrations can be utilized to indicate thevarious adjusted positions of compression springs 7' having differentspring characteristics.

Moreover, the compression spring 7' may be preliminarily stressed so asto produce a substantial force applied to the side strap 8, even whenthe pin 51 is securing the left end of the tube 6' to the aperturedesignated 1 of the backing 5'. In such case the extension of the spring7' is limited by engagement of the shoulder at the junction between theside strap 8 and its reduced portion 8" with the right side of thebridge 12 upstanding from the backing 5'. Such engagement of theshoulder with the bridge will establish one limit of the normal workingrange of the side strap, and the other limit of such range is reachedwhen the gradually inclined side of the buttress tooth 13b engages theleft side of the bridge 12. Further movement of the side strap 8 to theright will pull the buttress tooth beneath the bridge 12 to its rightside, effecting latching action of the limit latch formed by bridge 12and buttress tooth 13b in the manner described in connection with theappliance shown in FIGS. 25 and 26.

In the appliance of FIG. 52, the force applied by the force-producingunit 3" to the side strap 8 is produced by a flat spiral spring 7",received in a housing box 57 carried by the backing 5'. The outer endportion of such spring extends through a slot 58 in such housing and isconnected to the reduced extension 8" of the side strap 8 which has aconstruction similar to that shown in FIGS. 50 and 51. A tab projectingfrom the side of such casing remote from the slot 58 has in it anaperture that can be placed in registration with any selected one of theapertures 56 arranged in a row lengthwise of the backing 5' to adjustthe force produced by the spring 7" and applied to the side strap 8through the reduced extension 8".

The backing 5' may have calibrations 30" arranged alongside therespective apertures 56 to designate the force which would be producedby the spring 7' and applied to the side strap 8 corresponding to theadjusted position in which the pin 51 secures the casing tab to thebacking 5'. While the calibrations are shown as designating ounces offorce, the various apertures 56 could simply be designated by digits, asdiscussed in connection with the appliance shown in FIGS. 50 and 51. Theindex 31 also cooperates substantially with the end of the spring 7" ina manner similar to that described in connection with FIGS. 5 and 25 toindicate when the spring force being produced corresponds exactly to thecalibrations 30. The limit latch structure provided in this appliance isthe same as that shown in FIGS. 25, 26, 28, 29, 50 and 51 includingcooperating bridge 12 on backing 5' and buttress tooth 13b on strapextension 8".

The embodiment of the invention shown in FIGS. 53 to 58, inclusive, isgenerally similar to the embodiment shown in FIGS. 25 to 27, inclusive.The force-producing unit 3 includes the helical tension spring 7received in tube 6 carried by a backing 5.

In this instance the tube is restrained from lateral displacementrelative to the backing 5 by being lodged between posts 29" upstandingfrom the backing at opposite sides of the tube. The free ends of theposts are curved toward each other to restrain movement of the tube awayfrom the backing, but the posts are sufficiently flexible so that theirbent ends can be spread to enable the tube to be inserted between theposts by movement transversely of the length of the tube instead of itbeing necessary to move the tube lengthwise as required to assemble thetube beneath the arch 29' in the construction shown in FIGS. 25 and 26.

The intermediate strap 10 is shorter than such strap shown in FIGS. 25,26 and 27, because the modification of FIGS. 53 to 57 does not have anylimit latch including a buttress tooth 13b, but such limit latch couldbe provided in this embodiment of the invention if desired. As in theappliance shown in FIGS. 25, 26 and 27, movement of the intermediatestrap to the left is limited by engagement of stop rib 19 with the rightside of bridge 12".

A main feature of the modified structure shown in FIGS. 53 to 58 is thedisconnectible connection between the intermediate strap 10 and the sidestrap 8'. This connection has the same general type of structure as theconnection shown in FIGS. 25, 26 and 27 in including the bridge 18'spanning the end portion of the intermediate strap at the side of stoprib 19 remote from spring 7, which rib cooperates with a reversely-bentspring strip 20', 21' carried by the cooperating end of side strap 8'.The principal difference in the two structures is in the proportions ofthe parts and the manner in which they cooperate.

The structure of the connection shown in FIGS. 53 to 58, inclusive, isvery precise, enabling the minimum tension and the amount of movementbetween side strap 8' and intermediate strap 10 which will effectdisconnection of these strap members to be determined quite accurately.In order to be able to select most readily the predetermined minimumtension between strap 8' and strap 10 which will effect disconnection ofof the connection, it is preferred that the degree of such tension bedetermined almost entirely by the characteristics of the spring strip20', 21'. Consequently, bridge 18' with which such strip cooperates ismade of very rigid construction.

The bridge 18' has a deep arch as shown in FIG. 54, and its oppositeends are mounted on the widened end 17 of intermediate strap 10 byupwardly tapered walls 57 forming rigid connections to the intermediatestrap end. The rigidity of the widened end of the intermediate strap isalso increased by providing sidewalls 58 connecting the opposite ends ofthe stop rib 19 and the upwardly tapered walls 57 at the opposite endsof the bridge 18'.

The leaf spring 20', 21' shown by itself in FIG. 58 is arranged in theconnection to utilize both cantilever leaf spring characteristics andsemielliptical leaf spring characteristics. The flat base 20' of thespring strip is inserted through a slit in the side strap 8', so thatsuch flat base portion of the spring underlies the underside of the endportion of side strap 8' while the bowed strip portion of the springlies alongside the other, i.e. upper, face of the side strap. The lengthof the widened portion 17 of the intermediate strap 10 is shown as beingapproximately equal to the combined lengths of the spring portions 20'and 21'.

The proportions of the connection parts and the spring characteristicsof the spring 20', 21' should be quite exact so as to provide a knownprestressed condition of the spring when the connector parts have beenassembled into the relationship shown in FIGS. 54 and 55. The side strap8' is assembled with the intermediate strap 10 in the manner describedin connection with FIGS. 25, 26 and 27, and illustrated particularly inFIG. 27. In such assembly operation the end of side strap 8' is threadedbeneath the bridge 18' and moved from left to right, as seen in FIG. 53,until the assembling operation is completed, with the parts in thepositions shown in FIGS. 54 and 55.

During movement of the side strap 8' in the direction indicated by thearrow in FIG. 53 relative to the intermediate strap 10, the bowedportion 21' will engage the bridge 18' before the tip of side strap 8'passes to the right beyond the stop rib 19. In order for the side strap8' to move relative to the intermediate strap 10 from the position ofFIG. 53 to the position of FIGS. 54 and 55, it may be necessary for thecantilever spring characteristics of the spring bow 21' to be overcomecompletely and such spring bow pressed downward until its free endengages the side strap.

If the side strap 8' is pulled to the right relative to the intermediatestrap 10 from the relative positions of these parts shown in FIG. 53,the bridge 18' will apply a wedging force to the right inclined side ofthe spring bow 21 for depressing such side so that the side strap cancontinue to be moved to the right. It is preferred that the left end ofthe cantilever bowed spring leaf 21' be engaged with the upper side ofthe side strap 8' before such side strap has been pulled far enough tomove its tip beyond the right side of the stop rib 19.

The additional movement required before the tip of side strap 8' willsnap past the right side of stop rib 19 into the position shown in FIG.55 should require that the arch of the bowed portion 21' of the springbe depressed to some extent. In such event the spring will beprestressed to the extent of the pull required to bend the bowed portionof the spring into contact with the side strap 8', if the spring is ofcantilever type, plus the pull required to depress the arch of the bowspring in order to enable the side strap to move relative to theintermediate strap sufficiently to accomplish such snap actionengagement of the parts. The parts will be maintained in such engagementas shown in FIG. 55 thereafter, even though the pull on the side strap8' is discontinued. Further movement of the side strap to the rightrelative to the intermediate strap can thereafter be effected only byexerting an extending pull on such straps exceeding the pull required tobe exerted in order to assemble the parts to the relationship shown inFIG. 55.

The amount of pull required to be exerted on side strap 8' to displacethe side strap relative to the intermediate strap should be greater thanthe pull exerted on the side strap 8' by spring 7 within the normalworking range of the appliance. Thus a pull which will stretch spring 7from the solid-line position of the intermediate strap 10 to thebroken-line position of that figure, in which the shoulder 15' isengaged with the left side of bridge 12", will be insufficient to effectrelative extension or separating movement of the side strap 8' andintermediate strap 10. If a pull is exerted on the side strap 8'sufficiently exceeding the pull required to assemble the side strap andthe intermediate strap in the relationship shown in FIG. 55 with thespring bow 21' prestressed, the spring bow can be wedged under thebridge 18' and the side strap can move farther to the right relative tothe intermediate strap 10, as shown in FIG. 56.

During such further movement of the side strap 8' to the right, theintermediate strap is restrained from being moved by the side strap 8'because of the engagement of shoulder 15' with the left side of bridge12", as shown in FIG. 56. When the arch of the spring bow 21' has beendepressed by wedging action of the bridge 18' to the position shown inFIG. 56, the side strap can be moved easily to the right from theposition of FIG. 56 to the position of FIG. 57, in which the side strap8' is disconnected from the intermediate strap 10.

The extension movement of side strap 8' relative to intermediate strap10 beyond the position of FIG. 55 to disconnect the straps is verysmall, such as three to seven millimeters. For the usual orthodontictreatment the pull exerted by spring 7 is in the range of eight to 48ounces, that is, one-half a pound to three pounds. The spring bow 21'may have a preload of four pounds when the parts are in the positionshown in FIG. 55, which means that a steady pull of four pounds appliedto the side strap 8' will not shift that strap to the right relative tothe intermediate strap 10.

The spring 20',21' may be selected so that a steady pull of five poundsapplied to the side strap 8' will move such side strap relative tointermediate strap 10 to and through the position of FIG. 56 todisconnect the connection. A sudden sharp pull of considerably lessmagnitude could also effect movement of the side strap 8' to the rightfrom the position of FIG. 55 to disconnect the side strap from theintermediate strap. The spring 20',21' can be selected for disconnectionof the parts under loads of different magnitude depending on the type oftreatment for which the particular appliance is designed.

The apertures 9' in the side strap 8' of FIG. 54 are larger than theholes 9 in the side strap 8 of the appliance shown in FIGS. 25 to 27,for example, to facilitate connection of such side strap to the hook ofthe tie rod 2. Also such holes are shown as being numbered for recordpurposes in fitting the appliance to a particular patient.

FIGS. 59 to 63, inclusive, show connection components of an orthodonticappliance utilizing a negator as the force-producing member or unit. Anegator differs from a helical tension spring by providing a constanttension irrespective of its lengthwise position of adjustment. Thenegator includes a freely curled confined coil of flat, flexible springsteel or stainless steel strip formed in a curved configuration tendingto coil throughout the active portion of its length. The strip may beconstructed to produce a tension force of a particular degree byselecting the proper width or the thickness or both of the strip stock.The thicker the stock and the wider the stock the greater will be thetension force exerted by the negator.

The component connector shown in FIGS. 59 and 60 for connecting a neckband, as shown in FIG. 1, or a head strap, a shown in FIG. 2, to anintraoral device, such as a facebow, includes the backing 5 connected tothe neckband or headcap reaction unit and a side strap 8' havingapertures 9' for selective connection to a facebow. The negatorincluding the spring coil 59 and tongue 60 is connected by an S hook toan aperture in the end of an intermediate strap 10 of the type shown inFIGS. 53 and 55 to 57, inclusive. Such strap extends beneath a bridge12" carried by the backing 5. The intermediate strap carries the stoprib 19 and the bridge 18' mounted on the widened end 17 of theintermediate strap by upwardly tapered walls 57. The sidwalls 58 connectthe opposite ends of the stop rib 19 with the tapered walls 57 in thesame manner as shown in FIGS. 53 to 57.

Also, as shown in FIGS. 53 to 57, a spring leaf 20',21' having a flatbase 20 and an arched portion 21 extends through a slot in the end ofside strap 8' so as to cooperate with the bridge 18' for providing adisconnectible connection. Such spring and bridge cooperate in themanner described in connection with FIGS. 53 to 57 so as to bedisconnected when the reaction device, such as a neckband or a headcap,is moved away from an intraoral device, such as a facebow, beyond apredetermined distance. Under such circumstances, the shoulder 15' ofthe intermediate strap 10 will engage the left side of bridge 12', asshown in broken lines in FIG. 60, and further movement of the strap 8'to the right relative to the backing 5 will pull the spring 21' beneathbridge 18' and disconnect side strap 8' from intermediate strap 10 inthe manner indicated in broken lines in FIG. 60.

Upon disconnection of the strap 8' from the right end of theintermediate strap 19, the negator coil 59 will rewind to shift theintermediate strap 10 to the left until the stop rib 19 is drawn intocontact with the right side of bridge 12". Throughout such movement ofthe negator spring tongue 60 the negator coil will be confined withinthe housing 62 mounted on the backing 5 so that the negator will beretained in coiled condition.

In FIGS. 61 and 62 the negator type of connector component is shown asbeing connected to the end of a side strap 8 having a limit latch of thetype shown in FIGS. 28, 29, 46, 47 and 52, but not having adisconnectible connection. In this structure, the side strap 8 carries abuttress tooth 13b near its end connected by the S hook 61 to the tongue60 of the negator. Such buttress tooth has an inclined or a slopingsurface facing toward the bridge 12" upstanding from the backing 5 andbeneath which bridge the side strap 8 extends. This limit latch operatesin the manner described in connection with FIGS. 25 to 29 in that whenthe reaction device, such as the neckband or headcap, and the intraoraldevice, such as a facebow, are moved away from each other apredetermined distance, the buttress tooth will be pulled beneath thebridge 12" from its left side to its right side.

Movement of the reaction device and the force-applying device away fromeach other will be limited by engagement of the shoulder 15' on theenlarged end of the strap 8 with the left side of bridge 12". If theforce tending to move the reaction device and the intraoral device awayfrom each other is relieved, the negator will attempt to pull the sidestrap 8 toward the backing 5, but such movement will be interrupted byengagement of the abrupt or sheer side of the buttress tooth 13b withthe right side of the bridge 12". Consequently, the negator strip willbe held in partially uncoiled condition by the limit latch.

The abrupt or sheer side of the limit latch buttress tooth 13b can bereleased from the right side of the bridge 12" by swinging the sidestrap 8 sidewise in the manner shown and described in connection withFIG. 29. The buttress tooth can then be shifted to the left as seen inFIGS. 61 and 62 beneath the bridge 12' to enable the negator to recoilto the condition shown in full lines in FIG. 61. Such recoiling actionis limited by engagement of shoulders 63 of side strap 8 projectinglaterally beyond the extension 8" of reduced width on which the limitlatch buttress tooth 13b is mounted. The component connector will thenbe in condition for reconnection in the orthodontic appliance inoperative condition.

The component connector shown in FIG. 63 includes a negatorforce-producing unit of the same construction as described in connectionwith FIGS. 59 to 62. In addition, this connection includes both a limitlatch generally of the type described in connection with FIGS. 61 and 62and a disconnectible connection so that this combination is comparableto that shown in FIGS. 25 to 27. In this instance, however, thedisconnectible connection is of the specific type shown in FIGS. 53 to57, 59 and 60. Since the operation of the limit latch and of thedisconnectible connection have both been described in connection withFIGS. 25 to 29, 61 and 62 and in connection with FIGS. 53 to 57, 59 and60, further description of the limit latch and disconnectible connectionat this point is unnecessary.

It need merely be said that relative movement of the backing 5 and theside strap 8' lengthwise of such side strap does not alter the forceproduced by the negator coil 59 appreciably. The limit latch includingbuttress tooth 13b and bridge 12" will be designed with relation to thecharacteristics of the disconnectible connection spring 21' and bridge18' such that the limit latch buttress tooth 13b will be moved beneaththe bridge 12' to the right and shoulder 15' will engage the left sideof the bridge 12" to activate the limit latch before the leaf spring 21'will be pulled to the right beneath bridge 18' to disconnect side strap8' from intermediate strap 10.

Consequently, under some circumstances the limit latch of the connectorshown in FIG. 26 may be latched without the side strap 8' beingdisconnected from the intermediate strap 10. When the side strap 8' isdisconnected from the intermediate strap 10, however, such disconnectionwill occur only after the limit latch has been latched so that the sheerside of the buttress tooth 13b will bear against the right side of thebridge 12" to prevent the intermediate strap 10 from returning to theleft into the position of FIG. 63 so that the stop rib 19 will engagethe right side of the bridge 12". In order to reset the connection foruse, intermediate strap 10 can be swung, as shown in FIG. 29, or simplypushed to the left to enable the buttress tooth to move back beneath thebridge 12" to release the limit latch and thereafter the side strap 8'can be connected again to the intermediate strap in the manner shown anddescribed in connection with FIGS. 53 and 55.

FIGS. 64 to 68 illustrate a force-producing unit for connection in anorthodontic appliance between an orthodontic force-applying member and aheadgear. The force-applying member, which may be a J-hook, can beattached to an intraoral orthodontic appliance such as an arch wire, andthe headgear can be of the headcap type or neckstrap type. The J-hook102 shown in FIG. 64 projects beyond one end of the force-producing unit103, and the opposite end of such force-producing unit is connected tothe headcap 104.

The force-producing unit is mounted on a base or backing 105 andincludes a housing tube 106 which is preferably transparent and houses ahelical tension spring 107. A loop 108 extending from one end of thespring is secured by a staple 108' to the backing 105. The opposite endof spring 107 is connected to the shank of J-hook 102 by a swivel jointformed by a bead 109 slidably and rotatively threaded on such shank.Movement of the bead along the shank is limited by an enlargement 110 ofthe shank.

It is desirable for the connection between the shank of J-hook 102 andthe spring 107 to enable the J-hook shank to swivel freely relative tothe spring so that turning of the J-hook does not twist the spring. Suchfree swiveling is promoted by the bead 109 being of cylindrical shapewith its axis coinciding with the J-hook shank and having its end remotefrom enlargement 110 in abutment with the adjacent end of another bead111 also slidably and rotatively threaded on the shank of the J-hook.Such bead 111 may likewise be of cylindrical shape and arrangedcoaxially with bead 109 and the J-hook shank, although its end remotefrom bead 109 could be rounded complementally to the interior shape ofthe beehive end 112 of spring 107.

Whether the end of bead 111 can turn readily relative to the beehive end112 of spring 107 is really immaterial because the friction between theabutting ends of the two beads 109 and 111 will be negligible, enablingthe shank of J-hook 102 to turn with bead 109 easily relative to bead111, or to turn relative to bead 109. The enlargement 110 forming a headon the J-hook shank can simply be a portion of such shank which has beenswaged flat and thus expanded transversely of the shank. The beehiveformation of the spring end 112 engageable with the bead 111 provides avery effective connection between the J-hook and the spring 107 whichminimizes stress concentration and fatigue resulting from pulling of thespring in the extended condition shown in broken lines in FIG. 65 on theshank of J-hook 102.

The shank of the J-hook is guided for longitudinal sliding movementrelative to the base or backing 105 by extending through aperturedguides 113 and 114 spaced lengthwise of such backing. Guide 113 servesas a stop for housing tube 106 which encloses spring 107. The staple108' limits movement of the housing tube away from the stop 113. The endof the J-hook 102 remote from spring 108 is formed as an eye 115 thatcan be opened to hook around an intraoral orthodontic arch wire, forexample, or which can be fastened in any other conventional manner to anintraoral device. Such loop is sufficiently small that it can bethreaded through a slot 116 in guide 113 and a slot 117 in guide 114 sothat guides 113 and 114 can be formed integrally with the backing 105,such as by such backing and guides being molded of plastic material.Alternatively the end of guide 113 can be slotted as shown for receptionof the J-hook shank between the bifurcations of the guide by movement ofsuch shank transversely of its length, which would eliminate the needfor slot 116.

The spring 107 produces an orthodontic correcting force which istransmitted to an intraoral force-applying device through the J-hook102. The reaction to the orthodontic correcting force developed by thespring 107 is transmitted to the head and/or neck of the patient by aheadcap 104 or a neckband constituting force-reaction means. Theforce-producing unit 103 is connected to the force-reaction means 104 bya connection shown in FIG. 64, the details of which connection are shownin FIGS. 66, 67 and 68. The connection preferably is adjustable inlength in a direction parallel to the direction in which the orthodonticcorrecting force is exerted by spring 107.

Preferably the connection between the force-producing unit 103 and theforce-reaction means includes a strap or tongue 118, and a socket intowhich such tongue can be inserted and which will grip the tongue. Theparticular form of socket shown in FIGS. 64, 66, 67 and 68 includes aguide bridge 119 beneath which the tongue can be slid freely, as bestseen in FIG. 66, and a latch bridge 120 spaced lengthwise of the strap118 and the backing 105 from the guide bridge. Such bridges are integralwith the end portion of backing 105 remote from the guides 113 and 114,and such bridges can be molded integrally with the backing out ofplastic.

As shown in FIGS. 66 and 68, the passage beneath guide bridge 119 isdeeper than the greatest thickness of tongue 118. Such tongue is not ofuniform thickness, but its outer surface has a row of parallel grooves121 extending transversely of the length of the tongue and spacedlengthwise of it. The intervals between such grooves are selected tocorrespond to the increments by which it is desired to be able to adjustthe effective length of the connection between the force-producing unit103 and the force-reacting means 104.

Each tongue groove 121 is of trapezoidal cross section including asteeply inclined or abrupt wall 122 nearer the tip of the tongue and agradually sloping wall 123 farther from the tongue tip. The abruptbuttress wall may be at an angle of approximately 120° to the flatbottom of the groove, and the gradually sloping wall may be at an angleof approximately 150° relative to the flat bottom of the groove so thatsuch groove walls are mutually perpendicular. The spaced grooves in oneside of the tongue 118 form buttress lands or teeth 124 between suchgrooves which constitute linear ratchet teeth. The height of the passagebeneath latch bridge 120 when the bridge is in relaxed condition is lessthan the greatest thickness of the lands or teeth of the strap or tongue118. The tip 125 of the tongue is double beveled to guide movement ofsuch tip beneath the guide bridge 119 and the latch bridge 120. In orderto pass the tip of the strap through the passage beneath the latchbridge, it is necessary for such bridge to be flexed outward to thebroken line position shown in FIGS. 66 and 67. Wedging of the bridgeinto such flexed condition is facilitated by the corner 126 of the sideof the bridge adjacent to guide bridge 119 being chamfered as shown inFIGS. 66 and 68 at an angle preferably corresponding to the angles ofthe gradually sloping groove sides 123.

When the tongue 118 is pushed relative to the force-producing unitbacking 105 in the direction indicated by the arrow in FIG. 66, the tipof the tongue will first slide readily beneath the guide bridge 119 andthe wedge shaped tongue tip 125 will move beneath the latch bridge 120.If the tongue is then pushed with greater force, the outer bevel of thewedge shaped end 125 will engage the chamfered surface 126 of bridge 120and deflect the bridge outwardly, as indicated in broken lines in FIGS.66 and 67, sufficiently so that the leading land 124 of the tongue willpass beneath the latch bridge.

The width of the latch bridge is preferably slightly narrower than themaximum width of a tongue groove 121 so that when the tongue has beenpushed from the position of FIG. 66 to the position of FIG. 68 thebridge will be in registration with a groove 122 and will be relaxedfrom the flexed position shown in broken lines in FIGS. 66 and 67.Preferably there is little or no backlash between the tongue and bridge,but the proportions of the bridge and tongue groove should be such thatthe bridge is not appreciably flexed when it is in registration with atongue groove. While the latch bridge 120 is shown as being inregistration with the groove 121 of tongue 118 nearest its tip, thetongue can be pushed farther relative to the latch bridge in the samedirection until the tongue comes into registration with any successivegroove which is appropriate to establish the desired length of theconnection between the force-producing unit 103 and the headgear 104.

While the slope of each gradually sloping groove and land side 123 andchamfered corner 126 of the latch bridge 120 is such that engagement ofsuch a side with the chamfered corner of the bridge will enable thebridge to be wedged outward readily sufficiently to pass the lands orteeth 124 of the tongue beneath the bridge, the tongue cannot be movedas readily relative to the latch bridge in the opposite directionindicated by the arrow in FIG. 68. Greater resistance to movement of thetongue in this direction results from the corner 127 of the latch bridge120 remote from the guide bridge 119 being substantially square andbeing engaged by the abrupt wall 122 of a tongue groove 121 and buttressland 124.

If the abrupt side 122 of a groove 121 and land 124 and the corner 127of the latch bridge 120 were both square, it would be extremelydifficult for the tongue 118 to be moved in the direction indicated bythe arrow in FIG. 68 relative to the latch bridge. The angle of theabrupt side 122 of the adjacent buttress land and groove is selected toprovide the desired resistance to unlatching of the tongue 118 relativeto the latch bridge 120, the angle of 120° for the latch side 122 beingsuggested above as a preferred angle. Such angle should be selected sothat it will be necessary to exert a force of five pounds to ten pounds,preferably approximately seven pounds, lengthwise of the tongue in orderfor the abrupt land side to wedge the latch bridge 120 outward enoughthat the adjacent land or tooth 124 will pass in the direction of thearrow beneath the bridge to effect a latch-releasing operation.

In use the force-producing unit 103 and the headgear 104 can be movedtoward each other in the relationship shown in FIG. 64 by sliding thetongue 118 into the sprocket formed by the bridges 119 and 120 until thedesired relationship between the force-producing unit and theforce-reaction member is established. Shoulders 128 on the connection atthe root of the tongue 118 will limit shortening of the connection. Byselecting the proper length of connection, the headgear can be fitted tovarious patients by using the same size of force-producing unit and thesame size of head-engaging member or neck-engaging member, or at leastby providing a smaller selection of sizes than would be necessary if theconnector were not adjustable in effective length by altering thesetting of the linear ratchet formed by the connector strap tongue 118and latch bridge 120.

The position of the tongue 118 relative to the latch bridge 120 is setboth with reference to the size of the patient's head and with referenceto the degree of pull desired to be transferred by the force-producingunit 103 to the force-applying J-hook 102. The force produced by theforce-producing unit can be increased simply by shortening theconnection effected by the tongue and the latch bridge. Preferably thespacing between the adjacent grooves 121 corresponds to predeterminedchanges in the force increment produced by the spring 107.

In FIG. 65 calibrations 130 are shown on the base 105 designatingdifferent degrees of pull effected by the spring 107 in ounce units. Thespacing between the eight ounce designation and the 16 ounce designationcorresponds to the spacing between adjacent grooves 121 in tongue 118.The change in force produced by elongation of the spring is linear, sothat the spacing between the eight ounce calibration and the 16 ouncecalibration is the same as the spacing between the sixteen ouncecalibration and the 24 ounce calibration and the same as the spacingbetween the 24 ounce calibration and the 32 ounce calibration. In eachinstance, the calibration indicates the force being produced by thespring 107 when its end attached to the shank of J-hook 102 is alignedwith the respective calibration. In FIG. 65 the spring will produce apull of 32 ounces when the spring has been stretched to the broken lineposition shown in that figure in which the end of the spring is alignedwith the thirty-two ounce calibration.

In FIG. 69 the same type of adjustable length latching connector asdiscussed with relation to FIGS. 66, 67 and 68 is shown as being usedfor a somewhat different application. In this instance, theforce-producing unit is associated with a neckstrap 101 instead of aheadcap 104. In FIG. 64 the end plate 129 of the connector is stapled tothe headcap, whereas in FIG. 69 the connector end plate is stapled tothe neckband. In the arrangement of FIG. 69 the connector is assembledby sliding the force-producing unit base 105 in the direction of thearrow shown in that figure toward the anchored base of the connector sothat the tongue 118 will slide beneath the guide bridge 119 and thelatch bridge 120 until the desired length of the connection has beenestablished.

In the type of connection described with relation to FIGS. 66, 67 and68, the wedging action between the tongue 118 and the latch bridge 120has been effected by making the opposite sides of the grooves 121inclined. Alternatively, as shown in FIGS. 70 and 71, the tongue 131 canhave in it spaced transverse grooves 132 with square sides 133 and 134forming right angle corners to cooperate with chamfered corners of thelatch bridge 120'. The corner 126 of such bridge adjacent to the guidebridge 119 could be chamfered as described in connection with FIGS. 66and 68. The corner 136 of the latch bridge 120' remote from the guidebridge 119 would, however, also be abruptly chamfered instead of beingsquare like the corner 127 of the latch bridge 120 shown in FIGS. 66 and68.

When the tongue 131 is being moved relative to the backing 105 in thedirection indicated by the arrow in FIG. 70, a bevel of the doublebeveled end 125 would engage the chamfered corner 126 of the bridge 121and wedge such bridge outward to the broken line position shown in FIG.70 so that a land 135 could pass beneath the bridge as described inconnection with FIG. 66. The tongue 131 could then move into theposition shown in FIG. 71. If the tongue is moved farther in thedirection indicated by the arrow in FIG. 70 relative to the backing 105,the corner of a square groove side 133 would engage the chamfered corner126 of the bridge 120' to wedge the bridge outward sufficiently toenable the next land 135 to pass under such bridge.

The tongue 131 can be shifted relative to the backing 105 in thedirection indicated by the arrow in FIG. 70 as much as may be desired toestablish the proper length of the connection by engagement of the latchbridge 120' with a selected groove 132 comparable to the operationdescribed in connection with FIGS. 64 and 66. When the bridge 120' is inregistration with a groove 132, it is difficult to move the tongue 131relative to the backing 105 in the direction indicated by the arrow inFIG. 71. The corner of the square groove and land buttress side 134would engage the abrupt chamfer 136 of the bridge to deter movement ofthe tongue to the left.

The amount of resistance produced by such engagement will depend on theflexibility characteristics of the bridge 120' and the angle and extentof the abrupt chamfer 136. The steeper the abrupt chamfer is the greaterwill be the resistance to withdrawal of the tongue from beneath thelatch bridge. It is preferred that a pull within the range of 5 to 10pounds be required to withdraw the tongue, and the preferred degree ofpull required would be approximately seven pounds.

Release of the tongue 118 from the latch bridge 120 shown in FIG. 68, orrelease of the tongue 131 from the latch bridge 120' shown in FIG. 71,is a safety measure to effect disconnection of the force-producing unit103 and the force-reaction element engaging the wearer's head and/orneck. Consequently, it is desirable for the latch bridge to be inengagement with the groove of the tongue nearest its tip 125 when theheadgear is in operation. Therefore, after the desired adjustedrelationship between the tongue and the force-producing unit has beenestablished, any portion of the strap or tongue projecting beyond theside of latch bridge 120 or 120' remote from the guide bridge 119 shouldbe cut off through the bottom of the groove adjacent to that side of thelatch bridge.

In FIG. 72 the same type of linear ratchet connection as shown in FIGS.64, 66, 67 and 68 is used. In this instance, however, the connector endplate 129a stapled to the headcap 104 carries the guide bridge 119a andthe latch bridge 120a, instead of the tongue socket bridges beingcarried by the force-producing unit. The tongue 118a is then formed asan extension of the base 105a of the force-producing unit 103a. Thetongue 118a has spaced transverse grooves 121a separated by lands 124a.The tongue 118a cooperates with the bridges 119a and 120a in the samemanner as described for the coaction of the tongue 118 and the bridges119 and 120 in FIGS. 66 and 68. It is, therefore, evident that inutilizing the linear ratchet connection the mounting of the tongue andthe socket bridges can be interchanged when desired.

The force-producing unit 103a shown in FIGS. 72, 73 and 74 is somewhatdifferent from the force-producing unit shown in FIGS. 64 and 65. Thespring 107 used in such force-producing unit is the same as the springused in the force-producing unit of FIGS. 64 and 65. In this instance,however, the spring is enclosed in a protective housing of generallyrectangular cross section having parallel sides 137 and a connecting top138 in generally rectangular relationship. Barbed projections 139 on theedges of walls 137 remote from top 138 can be moved through slots 140 inthe base 105a to secure the cover to the base. While the connectionbetween the shank of J-hook 102 and the beehive 112 of the spring 107could be the same as illustrated in FIG. 65 and described in connectionwith that figure, FIG. 73 shows a somewhat different connection. In thisinstance a single bead 109a is fitted slidably on the J-hook shank andsuch bead can be of spherical or ellipsoidal shape. One end of such beadwould fit the interior of the beehive spring end 112, and the other endof such bead would bear against an enlargement 110a of the J-hook shank.Such enlargement could be produced simply by swaging opposite sides ofthe shank to produce flattened projections after the bead had beenplaced on the shank.

An end wall section 141 of the housing projects from one end of the base105a and has in its edge remote from the base a notch 142 for embracingthe shank of J-hook 102. A complemental end section 143 in the coverportion of the housing has a notch 144 complemental to notch 142 forcompleting a guide aperture for the J-hook shank when the housing isassembled from the exploded condition shown in FIG. 74 to the positioncovering the base shown in FIGS. 72 and 73. In the force-producing unitof FIGS. 72, 73 and 74 the loop 108 on the end of spring 107 is anchoredby being fitted over a post 145 between longer posts 146 upstanding in atransverse row from the base 105a, as shown in FIG. 74. The spring andJ-hook will be assembled with the base 105a before the cover isassembled with the base. The cover portion of the housing has apartition section 147 in registration with the backing posts 146 so thatsuch posts and partition section form a partition in the housing whenthe cover is assembled with the base.

In the force-producing unit of FIGS. 72, 73 and 74 reciprocation of theshank of J-hook 102 is guided by guides at opposite sides of spring 107instead of the guides being both at the same side of the spring as areguides 113 and 114 in FIG. 65. The cover partition section 147engageable with the ends of posts 146 has a notch 148 in its edgebetween such posts for receiving an extension 149 of the J-hook shank102 extending through such notch and between such posts beyond thespring-anchoring eye 108. By guiding the extended J-hook shank both byengagement in the notch 148 and in the two notches 142 and 144, theJ-hook shank is prevented from being swung relative to the base 105a byan off-center pull on the J-hook. Consequently, the J-hook shank isprevented from being swung into position pressing against the wearer'scheek.

The J-hook shank extension 149 is further guided by passing through anotch 150 in an additional partition section 151 aligned with partitionsection 152 in the cover having a notch 153 complemental to the notch150. Such partition sections 151 and 152 are at the side of posts 146remote from the housing end 141, 143. The sides of notches 150 and 153nearer the spring 107 are flared to guide the end of the J-hookextension 149 into the notches when the stretching of spring 107 isreduced from the highly stretched condition shown in broken lines inFIG. 73.

The housing of the force-producing unit is sufficiently long so that theJ-hook shank extension 149 will not project beyond the left end of thehousing cover when the spring 107 is in its most contracted positionshown in full lines in FIG. 73. The degree of extension of the springcorresponding to different degrees of pull produced by the spring isindicated by the calibration scale 130a shown on the force-producingunit housing top in FIGS. 72 and 74. The degree of force produced by thespring will be indicated by the calibration member with which the end ofthe stretched spring is aligned. A longitudinal slot can be provided inthe cover top 138 along the length of the calibrated portion forobservation of the position of the spring end.

Instead of securing the connector end plate 129 in FIG. 64 or 129a inFIG. 72 directly to a headcap 104 or to a neckstrap 101, as shown inFIG. 69, the force-producing unit can be connected by the connector to acomposite neckstrap and headcap generally of the type shown in U.S. Pat.No. 3,203,099 or in FIG. 3 of U.S. Pat. No. 3,571,930. In FIG. 75 a yokebow 154 is shown as connecting a neckband 155 and a headcap 156. Theconnection of the present invention can be connected between aforce-producing unit of the type shown in FIGS. 72 and 73 and such yokebow.

A connector end attachment plate 157 carries a guide bridge 119b and alatch bridge 120b in series arrangement to receive a tongue 118a, asindicated in broken lines in FIG. 76. An anchor lug 158 projectinglaterally from the connector plate can be fitted into any hole 159 of arow of holes extending lengthwise of the yoke bow 154. The anchor lugcan be headed and serve as a pivot to enable the connector endattachment plate 157 to swing or swivel into various angularly adjustedpositions, or the anchor lug can be expandable and secured in positionby a lug-expanding screw which will wedge the lug into a selectedaperture and secure the connector end plate against turning with respectto the yoke bow. The end plate connection and the back of the yoke bowcan be covered by a resilient pad 160.

In FIG. 77 a modified yoke bow construction includes the yoke bow 154ahaving one end secured to the neck band 155 and its other end secured tothe headcap 156. In this instance, instead of the yoke bow having in itspaced apertures to which a connector end plate can be anchored, aplurality of latch bridges 120c, 120d, 120e and 120f are formed integralwith the yoke bow at different locations, and perhaps at differentangles, along its length. The strap or tongue 118a of a force-producingunit such as shown in FIGS. 72 and 73 can be inserted beneath any one ofsuch bridges for completing a connection between the force-producingunit and the force-reaction means. Without providing guide bridges inconnection with the latch bridges shown in FIG. 77, it will usually bepossible for the force-producing unit to be swung angularly to a limitedextent relative to the latch bridge with which it is engaged.

In both the orthodontic device shown in FIGS. 75 and 76 and theorthodontic device shown in FIG. 77, it is possible to connect twoforce-producing units to the yoke bow if desired. The J-hook of one ofsuch units could be connected to an intraoral device such as an archwire on the upper teeth and the J-hook of the lower force-producing unitcould be connected to an intraoral device such as an arch wire on thelower teeth. With the apparatus of FIG. 75 two connector end plates 157could have their anchor lugs 158 engaged in two of the apertures 159,respectively, of the yoke bow. FIG. 77 shows a connector tongue 118asecured beneath the upper latch bridge 120c and a second connectortongue 118a in the process of being engaged with a lower latch bridge120e.

As explained previously, when the headgear has been fitted properly tothe patient and adjusted to provide the desired pull on the J-hook, anyprojecting portion of the connector strap or tongue beyond the latchbridge should be cut off. Thus, after the headgear shown in FIG. 77 hasbeen fitted properly to the patient, the portion of the tongue 118aanchored by latch bridge 120c beyond the groove exposed at the left ofsuch bridge would be cut off by cutting the tongue at the location ofsuch groove. The tongue would then be pulled out of the latch bridge anddisconnected from it by a pull produced by the force producing unitexceeding a predetermined value. The tongue could be reengaged with thelatch bridge in the manner described in connection with FIG. 66 torestore the connection in its original condition without structuralinjury to the interfitting components of the connection.

I claim:
 1. In an orthodontic appliance including force-reaction meansengageable with the wearer's head and/or neck, orthodonticforce-applying means for applying force to a jaw and connector meansconnecting the force-reaction means and the force-applying means andincluding resilient force-producing means for producing a yieldableforce applied to the force-applying means, the improvement comprisingmeans for providing relative movement of the force-reaction means andthe force-applying means away from each other free of the yieldableforce of the resilient force-producing means automatically in responseto relative movement of the force-reaction means and the force-applyingmeans away from each other beyond a predetermined limit.
 2. In anorthodontic appliance including force-reaction means engageable with thewearer's head and/or neck, orthodontic force-applying means for applyingforce to a jaw and resilient force-producing connector means connectingthe force-reaction means and the force-applying means for producing ayieldable force applied to the force-applying means, the improvementcomprising means for providing relative movement of the force-reactionmeans and the force-applying means free of the yieldable force of theresilient force-producing connector means automatic in response toincrease in the degree of resilient force applied by the resilientforce-producing connector means to the force-applying means beyond apredetermined limit.
 3. In the appliance defined in claim 2, theresilient force-producing connector means including spring means.
 4. Inan orthodontic appliance including force-reaction means engageable withthe wearer's head and/or neck, an orthodontic force-applying device forapplying force to a jaw, connector means connected to the force-applyingdevice and a resilient force-producing unit connecting theforce-reaction means and the connector means for exerting asubstantially linear force between such means tending to reduce thedistance between such means, the improvement comprising a connectionconnecting the resilient force-producing unit and one of the means andautomatically operable by relative movement of the resilientforce-producing unit and such one means in a direction substantiallyparallel to the direction of force exerted by the resilientforce-producing unit which movement increases the distance between theforce-reaction means and the connector means beyond a predeterminedlimit, to enable the force-reaction means and the connector means tomove farther away from each other free of the force of theforce-producing unit.
 5. In the appliance defined in claim 4, theconnection including two separable elements, a bridge carried by one ofsaid elements and a buttress member carried by the other of saidelements and movable beneath said bridge by application between said twoelements of any force exceeding a predetermined force.
 6. In theappliance defined in claim 4, the connection being disconnectible byapplication to the appliance of any force exceeding a predeterminedforce exerted in a direction substantially parallel to the direction offorce exerted by the resilient force-producing unit tending to increasethe distance between the force-reaction means and the connector means.7. In the appliance defined in claim 6, the connection including twoseparable elements, a bridge carried by one of said elements and a bowedspring carried by the other of said elements and movable beneath saidbridge automatically in response to application between said twoelements of such force exceeding the predetermined force.
 8. In theappliance defined in claim 7, the bowed spring being of the cantilevertype.
 9. In the appliance defined in claim 7, means for holding thebowed spring in engagement with the bridge in stressed condition.
 10. Inthe appliance defined in claim 4, the connection including two separableelements, spring means resisting separation of said two separableelements and means for holding said spring means stressed to a degreeless than the stress to which said spring means are subjected duringseparation of said two separable elements.
 11. In the appliance definedin claim 4, the connection including two separable elements, a bridgecarried by one of said elements and a buttress member carried by theother of said elements and movable beneath said bridge by relativemovement of the force-reaction means and the force-applying deviceexceeding a predetermined degree of movement in the direction increasingthe distance between the force-reaction means and the connector means.12. In the appliance defined in claim 4, the force-reaction meansincluding a neckband.
 13. In the appliance defined in claim 4, theforce-reaction means including a head-engageable member.
 14. In theappliance defined in claim 4, the force-reaction means including thecombination of a neckband and a head-engageable member, and tworesilient force-producing units independently connected, respectively,to said neckband and to said head-engageable member.
 15. In theappliance defined in claim 4, the connection connecting theforce-reaction means and the resilient force-producing unit.
 16. In theappliance defined in claim 4, the connection connecting the connectormeans and the resilient force-producing unit.
 17. In the appliancedefined in claim 4, the resilient force-producing unit and one of themeans being relatively movable, and a limit latch interposed between theresilient force-producing unit and such one means and latchableautomatically in response to predetermined relative movement of theresilient force-producing unit and such one means away from each otherto control return movement of the resilient force-producing unit andsuch one means toward each other by force exerted by the resilientforce-producing unit.
 18. In the appliance defined in claim 4, theresilient force-producing unit including a negator.
 19. In anorthodontic appliance including force-reaction means engageable with thewearer's head and/or neck, orthodontic force-applying means for applyingforce to a jaw and connector means connecting the force-reaction meansand the force-applying means and including resilient force-producingmeans for producing a yieldable force applied to the force-applyingmeans, the improvement comprising immobilizing means for maintaining theresilient force-producing means in a predetermined deflected conditionautomatically in response to relative movement of the force-reactionmeans and the force-applying means sufficient to move the resilientforce-producing means into such predetermined deflected condition. 20.In the appliance defined in claim 19, the resilient force-producing unitincluding a negator.
 21. In an orthodontic appliance including aforce-reaction component engageable with the wearer's head and/or neck,an orthodontic force-applying device for applying force to a jaw,resilient force-producing connector means connected to theforce-reaction component and to the force-applying device fortransmitting force therebetween, the improvement comprising theresilient force-producing connector means including a limit latchlatchable automatically in response to predetermined relative movementof the force-reaction component and the force-applying device away fromeach other for inhibiting unrestrained shortening of the resilientforce-producing connector means by force exerted by the resilientforce-producing connector means which would move the force-reactioncomponent and the force-applying device toward each other.
 22. In theappliance defined in claim 21, the limit latch being operable to preventappreciable movement of the force-reaction and the force- toward eachother.
 23. In the appliance defined in claim 22, the limit latch beingreleasable at will for return movement of the force-reaction componentand the force-apply device toward each other.
 24. In the appliancedefined in claim 22, the limit latch including a bridge and a buttressmember carried by the resilient force-producing connector means, saidbuttress member being movable beneath said bridge into latched positionby predetermined relative movement of the force-reaction component andthe force-applying device away from each other.
 25. In the appliancedefined in claim 24, the buttress member having an inclined surface forguiding the member for return movement under the bridge.
 26. In theappliance defined in claim 24, the buttress member having a cornerchamfered for guiding the member for return movement under the bridgewhen the member is swung relative to the bridge.
 27. In the appliancedefined in claim 21, the limit latch including a bridge and a springcarried by the resilient force-producing connector means, said springbeing movable beneath said bridge into latched position by predeterminedrelative movement of the force-reaction component and the force-applyingdevice away from each other.
 28. An orthodontic appliance comprising aforce-reaction component engageable with the wearer's head and/or neck,an orthodontic force-applying component for applying force to a jaw,connector means connecting said force-reaction component and saidforce-applying component and including a variable length resilientforce-producing unit, increase in length of said resilientforce-producing unit enabling said two components to move away from eachother opposed by force produced by said force-producing unit, and safetymeans interposed between said resilient force-producing unit and one ofsaid components for inhibiting, automatically in response to saidresilient force-producing unit exerting a force greater than apredetermined force, unrestrained snapback of said resilientforce-producing unit moving said two components toward each other. 29.An orthodontic appliance comprising force-reaction means engageable withthe wearer's head and/or neck, an orthodontic force-applying device forapplying force to a jaw, a resilient force-producing unit connected tosaid force-reaction means, and a connector strap connected to saidorthodontic force-applying device and having linear ratchet meansengageable with said resilient force-producing unit for varying therelationship between said connector strap and said resilientforce-producing unit.
 30. An orthodontic appliance comprisingforce-reaction means engageable with the wearer's head and/or neck, anorthodontic force-applying device for applying force to a jaw, connectormeans connected to said force-applying device, a spring-force unitconnecting said force-reaction means and said connector means andincluding elongated spring means having one end connected to saidconnector means, adjusting means displaceable relative to saidforce-reaction means and connected to said spring means at a locationremote from said one end of said spring means connected to saidconnector means for adjusting the length of said spring means to alterthe preliminary stress in said spring means and anchorable relative tosaid force-reaction means to select a spring adjustment corresponding toan average force of a predetermined value, said connector means and saidspring-force unit being relatively movable, and movement-limiting meanslimiting relative movement of said connector means and said spring-forceunit to a displacement less than the extent to which said adjustingmeans can be displaced relative to said force-reaction means foraltering the preliminary stress of said spring means.
 31. The appliancedefined in claim 30, the spring means including a helical spring. 32.The appliance defined in claim 31, the adjusting means including aspring anchor strap connected to the helical spring and having aplurality of apertures therein corresponding respectively to differentpreliminarily stressed conditions of the spring, and the spring-forceunit including an anchor pin fixed relative to the force-reaction meansand engageable in a selected aperture of said strap and keeper meansengageable with the portion of said strap at the side of said anchor pinremote from the spring.
 33. The appliance defined in claim 32, thekeeper means including a slot for receiving a portion of the strap. 34.The appliance defined in claim 32, the keeper means including acantilever bridge fixed relative to the force-reaction means at the sideof the pin remote from the helical spring for receiving a portion of thestrap beneath said bridge.
 35. The appliance defined in claim 34, thefree end of the cantilever bridge having an under bevel.
 36. Theappliance defined in claim 34, the free end of the cantilever bridgehaving an under bevel skewed so as to be inclined from the side of thebridge next to the pin away from the root end of the bridge.
 37. Theappliance defined in claim 34, the keeper means including a backing, abuttress projection upstanding from said backing at a location spacedfrom the root of the cantilever bridge and adjacent to the free end ofsuch bridge, the height of said projection being less than the maximumheight of the bridge, and such projection having a side inclined upwardtoward the free end of the bridge.
 38. The appliance defined in claim34, the keeper means including two cantilever bridges arranged in seriesalignment, spaced lengthwise of the spring anchor strap, and said twobridges having cantilever portions projecting from root portions inopposite directions respectively transversely of the spring anchorstrap.
 39. The appliance defined in claim 34, the pin being an uprightcantilever pin substantially straight throughout its length.
 40. Theappliance defined in claim 30, the adjusting means including an anchorstrap having a plurality of ratchet teeth spaced along its length and anelongated bridge having its length extending transversely of said anchorstrap for receiving said anchor strap therebeneath with a selectedratchet tooth engaging an edge of said bridge.
 41. The appliance definedin claim 31, calibration means cooperating with an end of the helicalspring for indicating the degree to which the spring is preliminarilystressed.
 42. The appliance defined in claim 30, the spring meansincluding a helical tension spring.
 43. The appliance defined in claim30, the spring means including a helical compression spring.
 44. Theappliance defined in claim 30, the spring means including a spiralspring.
 45. In an orthodontic appliance including force-reaction meansengageable with the wearer's head and/or neck, an orthodonticforce-applying device for applying force to the wearer's jaw, connectormeans connected to the force-applying device, and a spring-force unitconnecting the force-reaction means and the connector means andincluding a helical tension spring and a tube enclosing such spring, theimprovement comprising the helical tension spring being preliminarilystressed, and the tube being precurved and rigid to deter buckling ofthe tube by force of the preliminarily-stressed helical tension spring.46. An orthodontic appliance comprising force-reaction means engaeablewith the wearer's head and/or neck, an orthodontic force-applying devicefor applying force to a jaw, and force-producing connector meansconnecting said force-reaction means and said force-applying device,said connector means including two connecting elements, one of saidelements being elongated, said connecting elements having meansinterengageable by relative movement lengthwise of said elongatedelement to transmit force between said force-reaction means and saidforce-applying device, said connecting elements being separable bycontinued relative movement thereof in the same direction withoutappreciable structural injury to said interengageable means, saidseparated interengageable means being again interengageable by relativemovement of said two connecting elements lengthwise of said elongatedelement to reconnect said force-reaction means and said force-applyingdevice by said interengageable means for again transmitting forcebetween said force-reaction means and said force-applying device. 47.The appliance defined in claim 46, the elongated connecting elementincluding a strap having a plurality of ratchet teeth spaced along itslength and a bridge for receiving said strap therebeneath with aselected ratchet tooth engaging an edge of said bridge.
 48. Theappliance defined in claim 47, the teeth being successively engageablewith the bridge edge by relative lengthwise movement of the twoconnecting elements in the same direction.
 49. The appliance defined inclaim 40, the elongated connecting element having a tongue and the otherconnecting element having a bridge, said tongue being movable lengthwisebeneath said bridge and carrying projecting means engageable with saidbridge constituting same direction for connecting the connectingelements.
 50. The appliance defined in claim 49, the projecting meansincluding a spring.
 51. The appliance defined in claim 50, the springincluding a bowed spring engageable with the bridge.
 52. The appliancedefined in claim 51, means for holding the bowed spring relative to thebridge in stressed condition.
 53. The appliance defined in claim 49, theprojecting means including a buttress member engageable with an edge ofthe bridge.
 54. The appliance defined in claim 49, means for deterringmovement of the projecting means away from the bridge by relativemovement of the connecting elements in the same direction as they weremoved relatively for engaging the projecting means with the bridge. 55.The appliance defined in claim 54, the means for deterring movement ofthe projecting means away from the bridge including a rib extendingtransversely of the strap and engageable by the end of such strap torestrain movement of the projecting means away from the bridge.
 56. Theappliance defined in claim 49, a spring-urged member carried by theelement having the bridge and engageable by the strap for deterringmovement of the strap relative to the bridge.
 57. An orthodonticappliance comprising force-reaction means engageable with the wearer'shead and/or neck, an orthodontic force-applying device for applyingforce to a jaw, connector means connected to said force-applying device,a resilient force-producing unit connecting said force-reaction meansand said connector means, and linear ratchet means for adjusting theconnection of said resilient force-producing unit to one of said means.58. In an orthodontic appliance including force-reaction meansengageable with the wearer's head and/or neck, an orthodonticforce-applying device for applying force to a jaw, a tension member anda resilient force-producing unit, the tension member and the resilientforce-producing unit being connected between the force-reaction meansand the force-applying device, the improvement comprising adisconnectible connection connecting the resilient force-producing unitand the tension member and having interfitting separable members whichare disengageable at a predetermined location by application to thetension member and the resilient force-producing unit of a force awayfrom each other exceeding a predetermined amount to separate theforce-reaction means from the force-applying device, and said separablemembers being reengageable to reconnect the resilient force-producingunit and the tension member.
 59. In an orthodontic appliance includingband means engageable with the wearer's head and/or neck, an orthodonticforce-applying device and connector means connecting the band means andthe force-applying device, the improvement comprising the connectormeans including two elongated connecting elements interengageable byrelative lengthwise movement of said elements in one direction and meansinterengageable between said connecting elements for deterring relativelengthwise movement thereof in the opposite direction.
 60. Anorthodontic appliance including force-reaction means and orthodonticforce-applying means, comprising a resilient, stress-limiting connectionconnecting the force-reaction means and the force-applying means andincluding a tension member, a resilient force-producing unit and aconnection connecting said resilient force-producing unit and saidtension member which is disconnectible by exertion of pulling force onsaid connection exceeding a predetermined amount.
 61. In an orthodonticappliance including force-reaction means and orthodontic force-applyingmeans, a resilient connection connecting the force-reaction means andthe force-applying means and comprising a tension member, a resilientforce-producing unit, and a connection connecting said resilientforce-producing unit and said tension member and includinginterengageable elements disconnectible without structural injury bymovement of said tension member and said resilient force-producing unitaway from each other exceeding a predetermined distance, saidinterengageable elements when disconnected being again interengageableto restore the same connection.
 62. In an orthodontic applianceincluding force-reaction means and orthodontic force-applying means, aconnection connecting the force-reaction means and the force-applyingmeans and comprising a first member carrying a bridge, and a secondmember having a spring normally engaging said bridge to limit relativemovement of said members and movable beneath said bridge automaticallyin response to application between said members of any force exceeding apredetermined force.
 63. An orthodontic headgear for applying correctiveforces to a patient undergoing orthodontic treatment comprisingsupportmeans adapted to fit a patient's head and/or neck, resilient meansassociated with said support means and adapted to produce a restoringforce, and coupling means in force-applying relationship with saidresilient means, adapted for engagement with an orthodontic applianceadapted to be movable with respect to said support means as saidresilient means is activated to produce such restoring force andincluding means for providing relative movement of the orthodonticappliance and said support means free of the force of said resilientmeans automatically in response to relative movement of the orthodonticappliance and the support means away from each other beyond apredetermined limit.
 64. An orthodontic headgear for applying correctiveforces to a patient undergoing orthodontic treatment comprisingsupportmeans adapted to fit a patient's head and/or neck, resilient meansassociated with said support means and adapted to produce a restoringforce, and coupling means in force-applying relationship with saidresilient means, adapted to be movable with respect to said supportmeans as said resilient means is activated to produce such restoringforce, adapted for attachment to an orthodontic appliance and includinginterengageable elements disconnectible without structural injury byrelative movement of the orthodontic appliance and said resilient meansaway from each other exceeding a predetermined distance in a directionsubstantially parallel to the direction in which the restoring force isexerted, said interengageable elements when disconnected being againinterengageable to restore the same connection.
 65. An orthodonticheadgear for applying corrective forces to a patient undergoingorthodontic treatment comprisingsupport means adapted to fit a patient'shead and/or neck, resilient means associated with said support means andadapted to produce a restoring force, coupling means in force-applyingrelationship with said resilient means and adapted to be movable withrespect to said support means as said resilient means is activated toproduce such restoring force, said coupling means being adapted toengage an orthodontic appliance, and immobilizing means for maintainingsaid resilient means in a predetermined deflected conditionautomatically in response to relative movement of the orthodonticappliance and said support means sufficient to move said resilient meansinto such predetermined deflected condition.
 66. In the orthodonticappliance defined in claim 61, the resilient force-producing unitincluding a negator.
 67. An orthodontic appliance comprisingforce-reaction means engageable with the wearer's head and/or neck, anorthodontic force-applying device for applying force to a jaw, resilientforce-producing means connected to said force-applying device, and aconnector including a tongue connected to one of said means and a linearratchet device connected to said tongue and to the other of said meansfor varying the relationship between said force-reaction means and saidresilient force-producing means.
 68. An orthodontic appliance comprisingforce-reaction means engageable with the wearer's head and/or neck,orthodontic force-applying means for applying force to a jaw, aresilient force-producing unit connected to one of said means, and aconnection connecting said resilient force-producing unit to the otherof said means and including a tongue having a transverse groove and alatch bridge beneath which said tongue is insertable for engagement ofsaid latch bridge in said groove, said groove and said latch bridgehaving cooperating wedging surfaces at opposite sides of said latchbridge, a wedging surface at one side of said latch bridge being lessabrupt than a wedging surface at the other side of said latch bridgeenabling said tongue to be moved relative to said latch bridge in onedirection by application of a lesser force than required to move saidtongue relative to said latch bridge in the opposite direction.
 69. Theappliance defined in claim 68, in which wedging surfaces at oppositesides of the latch bridge are both inclined with relation to thedirection of relative movement of the tongue and the latch bridge. 70.The appliance defined in claim 69, in which wedging surfaces at oppositesides of the latch bridge include opposite sides of a tongue groove. 71.The appliance defined in claim 69, in which wedging surfaces at oppositesides of the latch bridge include opposite chamfered sides of the latchbridge.
 72. The appliance defined in claim 68, and a guide bridgebeneath which the tongue is insertable which is located at the side ofthe latch bridge remote from the side of the latch bridge at which themore abrupt wedging surface is located.
 73. An orthodontic appliancecomprising force-reaction means engageable with the wearer's head and/orneck and including a yoke bow, orthodontic force-applying means forapplying force to a jaw, a resilient force-producing unit connected tosaid orthodontic force-applying means, and a connection connecting saidresilient force-producing unit and said yoke bow including a latchbridge and a tongue insertable beneath said latch bridge and carryingprojecting means engageable with said latch bridge for connecting saidyoke bow and said resilient force-producing unit.
 74. The appliancedefined in claim 73, the tongue having a transverse groove forengagement of the latch bridge in said groove, said groove and the latchbridge having cooperating wedging surfaces at opposite sides of thelatch bridge, a wedging surface at one side of the latch bridge beingless abrupt than a wedging surface at the other side of the latch bridgeenabling the tongue to be moved relative to the latch bridge in onedirection by application of a lesser force than required to move thetongue relative to the latch bridge in the opposite direction.
 75. Theappliance defined in claim 73, in which the latch bridge is carried bythe yoke bow, and the tongue is carried by the resilient force-producingunit.
 76. The appliance defined in claim 75, including an attachmentplate carried by the yoke bow and carrying the latch bridge.
 77. Theappliance defined in claim 76, including a guide bridge carried by theattachment plate in alignment with the latch bridge and at the side ofthe latch bridge nearer the resilient force-producing unit.
 78. Theappliance defined in claim 75, including a plurality of latch bridgescarried by the yoke bow and arranged generally in a row extendinglengthwise of the yoke bow.
 79. An orthodontic appliance comprisingforce-reaction means engageable with the wearer's head and/or neck, aforce-applying member for applying force to a jaw, a resilientforce-producing unit connected to said force-applying member forexerting force thereon, and a connection connecting said force-reactionmeans and said resilient force-producing unit and including linearratchet means engageable in different positions to vary the forceexerted by said force-producing unit on said force-applying member. 80.The orthodontic appliance defined in claim 79, in which the linearratchet means includes a latch bridge and a tongue having its endportion inserted beneath and projecting beyond said latch bridge with abuttress surface engageable with the side of said latch bridge nearerthe end of said tongue and disconnectible from said latch bridge byapplication to the connection of a force exceeding a predetermined forcetending to separate the force-reaction means and the resilientforce-producing unit.
 81. The orthodontic appliance defined in claim 79,the resilient force-producing unit including a helical spring having abeehive end remote from the force-reaction means, the force-applyingmember including a shank extending lengthwise through said beehivespring end longitudinally of said spring, and a bead rotatively mountedon said shank and engaged in said beehive spring end for enabling theforce-applying member to swivel relative to said beehive spring end. 82.The orthodontic appliance defined in claim 81, the portion of the shankwithin the beehive spring end having an enlargement, and a second beadrotatively mounted on the shank between said shank enlargement and thebead engaged within the beehive spring end.
 83. An orthodontic appliancecomprising force-reaction means engageable with the wearer's head and/orneck, orthodontic force-applying means for applying force to a jaw, aresilient force-producing unit connected to one of said means, saidresilient force-producing unit including a helical coil tension springhaving a beehive end, and a connection connecting said resilientforce-producing unit and the other of said means and including a rodextending through said beehive spring end and a bead rotatively mountedon said rod and engaged in said beehive spring end.
 84. The orthodonticappliance defined in claim 83, the portion of the rod received withinthe spring end having an enlargement, and a second bead rotativelymounted on the rod between said rod enlargement and the bead engagedwithin the beehive spring end.
 85. An orthodontic appliance comprisingforce-reaction means engageable with the wearer's head and/or neck, aresilient force-producing unit connected to said force-reaction meansand including a helical spring and orthodontic force-applying means forapplying force to a jaw including a rod extending lengthwise throughsaid spring for receiving force therefrom for application to the jaw,said resilient force-producing unit including two guide means atopposite ends of said spring engageable with portions of said rod atopposite ends of said spring for deterring swinging of said rod relativeto said resilient force-producing unit.
 86. The orthodontic appliancedefined in claim 59, in which the connection includes interfittingelements disconnectible without structural injury by exertion of pullingforce on the connection exceeding a predetermined amount and whichinterfitting elements can again be interfitted to restore the sameconnection, one of said interfitting elements being a spring element.87. The orthodontic appliance defined in claim 86, in which the springelement includes a bowed portion.
 88. In the appliance defined in claim4, the resilient force-producing unit including a helical spring.
 89. Inthe appliance defined in claim 88, the helical spring being a helicaltension spring.
 90. In an orthodontic appliance including aforce-reaction component engageable with a wearer's head and/or neck, aforce-applying component and resilient force-producing means connectedbetween the force-reaction component and the force-applying componentfor biasing the force-applying component to apply force to the wearer'sjaw, the force-applying component being movable relative to theforce-reaction component between a normal position in which force isapplied to the jaw by the force-applying component and a relievedposition in which no force is applied to the jaw by the force-applyingcomponent, the improvement comprising means for exerting a forceopposing the biasing force exerted by the force-producing means when theforce-applying component is in relieved position to control its movementfrom relieved position toward normal position.
 91. The method ofassembling an orthodontic appliance including force-reaction meansengageable with the wearer's head and/or neck, an orthodonticforce-applying device for applying force to a jaw and force-producingconnector means for connecting the force-reaction means and theforce-applying device, such connector means including two connectingelements one of such elements being elongated and such connectingelements having interengageable means for transmitting force between theforce-reaction means and the force-applying device, which methodcomprises interengaging the connecting elements by relative movementlengthwise of the elongated connecting element and thereby engaging theinterengageable means to transmit force between the force-reaction meansand the force-applying device, continuing relative movement of theconnecting elements in the same relative direction and therebyseparating such connecting elements without structural injury, andsubsequently repeating the relative movement of the connecting elementslengthwise of the elongated element and thereby reconnecting theforce-reaction means and the force-applying device by the two connectingelements for again transmitting force between the force-reaction meansand the force-applying device.